Problem with uPnP

Hi

On my LAN I have 3 Win10 devices that reach to open upnp portforward in the gateway. Another device (armf raspbian) fails. Any idea please ? I changed config (NatLeaseMinutes=6 & NatRenewalMinutes=3) so that there is more log entries and started STTRACE=upnp syncthing &. All devices are 1.6.1

2020-06-15 11:31:43 My ID: SHORT-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH
2020-06-15 11:31:44 Single thread SHA256 performance is 45 MB/s using crypto/sha256 (45 MB/s using minio/sha256-simd).
2020-06-15 11:31:45 Hashing performance is 40.99 MB/s
2020-06-15 11:31:45 Overall send rate is unlimited, receive rate is unlimited
2020-06-15 11:31:45 Using discovery server https://discovery.syncthing.net/v2/?noannounce&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
2020-06-15 11:31:45 Ready to synchronize "Folder1" (Folder1-ID) (receiveonly)
2020-06-15 11:31:45 Ready to synchronize "Folder2" (Folder2-ID) (sendreceive)
2020-06-15 11:31:45 Relay listener (dynamic+https://relays.syncthing.net/endpoint) starting
2020-06-15 11:31:45 TCP listener ([::]:32571) starting
2020-06-15 11:31:45 Using discovery server https://discovery-v4.syncthing.net/v2/?nolookup&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
2020-06-15 11:31:45 ...
2020-06-15 11:31:45 Completed initial scan of sendreceive folder "Folder2" (Folder2-ID)
2020-06-15 11:31:45 Using discovery server https://discovery-v6.syncthing.net/v2/?nolookup&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
2020-06-15 11:31:45 GUI and API listening on 127.0.0.1:8384
2020-06-15 11:31:45 Access the GUI via the following URL: https://127.0.0.1:8384/
2020-06-15 11:31:45 My name is "Raspi"
2020-06-15 11:31:45 Device WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN101" at [dynamic]
2020-06-15 11:31:45 Device WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN102" at [dynamic]
2020-06-15 11:31:45 Device WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN103" at [dynamic]
2020-06-15 11:31:46 Completed initial scan of receiveonly folder "Folder1" (Folder1-ID)
2020-06-15 11:31:46 Established secure connection to WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [IpV6-0]:39498-[IpV6-1]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2020-06-15 11:31:46 Device WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN101" at [IpV6-0]:39498-[IpV6-1]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2020-06-15 11:31:46 Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
2020-06-15 11:31:46 Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
2020-06-15 11:31:46 Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
2020-06-15 11:31:46 Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
2020-06-15 11:31:46 Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
2020-06-15 11:31:46 Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
2020-06-15 11:31:46 Established secure connection to WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:50444-192.168.0.15:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256
2020-06-15 11:31:46 Device WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN102" at 192.168.0.49:50444-192.168.0.15:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256
2020-06-15 11:31:47 Established secure connection to WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:45912-192.168.0.20:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2020-06-15 11:31:47 Device WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN103" at 192.168.0.49:45912-192.168.0.20:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
2020-06-15 11:31:56 Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
2020-06-15 11:31:56 Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
2020-06-15 11:32:00 Detected 1 NAT service
2020-06-15 11:32:15 Joined relay relay://46.223.16.186:34617
2020-06-15 11:34:56 Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
2020-06-15 11:34:56 Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
2020-06-15 11:34:56 Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
2020-06-15 11:34:56 Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
2020-06-15 11:34:56 Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
2020-06-15 11:34:56 Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
2020-06-15 11:35:06 Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
2020-06-15 11:35:06 Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.

Thank you

I suggest you get the logs from the console, not the UI as it seems to have skipped over the part that matters (web ui only shows the tail of the logs).

Here is one Audrius

	[start] 2020/06/15 14:17:55.834481 main.go:588: INFO: syncthing v1.6.1 "Fermium Flea" (go1.14.4 linux-arm) deb@build.syncthing.net 2020-06-02 09:49:22 UTC
	[SHORT] 2020/06/15 14:17:55.978624 syncthing.go:159: INFO: My ID: SHORT-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH
	[SHORT] 2020/06/15 14:17:56.911693 sha256.go:87: INFO: Single thread SHA256 performance is 45 MB/s using crypto/sha256 (45 MB/s using minio/sha256-simd).
	[SHORT] 2020/06/15 14:17:57.533589 syncthing.go:191: INFO: Hashing performance is 41.00 MB/s
	[SHORT] 2020/06/15 14:17:57.534210 limiter.go:165: INFO: Overall send rate is unlimited, receive rate is unlimited
	[SHORT] 2020/06/15 14:17:57.534579 syncthing.go:289: INFO: Using discovery server https://discovery.syncthing.net/v2/?noannounce&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
	[SHORT] 2020/06/15 14:17:57.534938 relay_listen.go:63: INFO: Relay listener (dynamic+https://relays.syncthing.net/endpoint) starting
	[SHORT] 2020/06/15 14:17:57.534973 syncthing.go:289: INFO: Using discovery server https://discovery-v4.syncthing.net/v2/?nolookup&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
	[SHORT] 2020/06/15 14:17:57.535019 tcp_listen.go:62: INFO: TCP listener (0.0.0.0:32571) starting
	[SHORT] 2020/06/15 14:17:57.535497 lowlevel.go:756: INFO: Stored folder metadata for "Folder2-ID" is 442284h17m57.535408174s old; recalculating
	[SHORT] 2020/06/15 14:17:57.535659 syncthing.go:289: INFO: Using discovery server https://discovery-v6.syncthing.net/v2/?nolookup&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
	[SHORT] 2020/06/15 14:17:57.542068 model.go:366: INFO: Ready to synchronize "Folder2" (Folder2-ID) (sendreceive)
	[SHORT] 2020/06/15 14:17:57.542464 model.go:366: INFO: Ready to synchronize "Folder1" (Folder1-ID) (receiveonly)
	[SHORT] 2020/06/15 14:17:57.545377 folder.go:689: INFO: Completed initial scan of sendreceive folder "Folder2" (Folder2-ID)
	[SHORT] 2020/06/15 14:17:58.045239 api.go:363: INFO: GUI and API listening on 127.0.0.1:8384
	[SHORT] 2020/06/15 14:17:58.045320 api.go:364: INFO: Access the GUI via the following URL: https://127.0.0.1:8384/
	[SHORT] 2020/06/15 14:17:58.045454 syncthing.go:350: INFO: My name is "Raspi"
	[SHORT] 2020/06/15 14:17:58.045519 syncthing.go:353: INFO: Device WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN101" at [dynamic]
	[SHORT] 2020/06/15 14:17:58.045558 syncthing.go:353: INFO: Device WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN102" at [dynamic]
	[SHORT] 2020/06/15 14:17:58.045593 syncthing.go:353: INFO: Device WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN103" at [dynamic]
	[SHORT] 2020/06/15 14:17:58.045627 syncthing.go:353: INFO: Device REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "Remote" at [dynamic]
	[SHORT] 2020/06/15 14:17:58.203011 folder.go:689: INFO: Completed initial scan of receiveonly folder "Folder1" (Folder1-ID)
	[SHORT] 2020/06/15 14:17:58.449825 service.go:326: INFO: Established secure connection to WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:52176-[2a01:e0a:WIN:101:IP:v6]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:17:58.450330 model.go:1788: INFO: Device WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN101" at [2a01:e0a:My::IP:v6]:52176-[2a01:e0a:WIN:101:IP:v6]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:17:58.550080 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:17:58.550466 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:17:58.550843 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:17:58.551137 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:17:58.551527 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:17:58.551784 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:17:58.801819 service.go:326: INFO: Established secure connection to WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:42138-192.168.0.15:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256
	[SHORT] 2020/06/15 14:17:58.801921 model.go:1788: INFO: Device WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN102" at 192.168.0.49:42138-192.168.0.15:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256
	[SHORT] 2020/06/15 14:17:59.370709 service.go:326: INFO: Established secure connection to WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:53614-[2a01:e0a:WIN:103:IP:v6:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:17:59.370968 model.go:1788: INFO: Device WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN103" at [2a01:e0a:My::IP:v6]:53614-[2a01:e0a:WIN:103:IP:v6:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:18:00.179855 service.go:326: INFO: Established secure connection to REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:33602-RemoteIPv4:22290/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:18:00.180272 model.go:1788: INFO: Device REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.7.0-rc.1" named "Remote" at 192.168.0.49:33602-RemoteIPv4:22290/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:18:08.696296 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:18:08.729224 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:18:12.736759 service.go:67: INFO: Detected 1 NAT service
	[SHORT] 2020/06/15 14:18:26.812452 static.go:68: INFO: Joined relay relay://212.47.253.154:22067
	[SHORT] 2020/06/15 14:21:08.730567 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:21:08.730770 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:21:08.731262 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:21:08.731382 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:21:08.731556 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:21:08.731813 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:21:18.738021 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:21:18.738234 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:24:18.739455 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:24:18.740026 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:24:18.740219 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:24:18.740415 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:24:18.740833 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:24:18.741014 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:24:28.746875 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:24:28.747227 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:27:28.748524 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:27:28.749164 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:27:28.749532 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:27:28.749636 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:27:28.750091 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:27:28.750312 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:27:38.755889 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:27:38.756140 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:30:38.757381 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:30:38.757626 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:30:38.757925 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:30:38.758118 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:30:38.758359 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:30:38.758529 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:30:48.764205 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:30:48.764353 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:33:48.765522 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:33:48.765757 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:33:48.766372 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:33:48.766591 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:33:48.766828 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:33:48.767000 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:33:58.772947 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:33:58.773153 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:34:25.537617 relay_listen.go:123: INFO: Relay listener (dynamic+https://relays.syncthing.net/endpoint) shutting down
	[SHORT] 2020/06/15 14:34:25.539036 static.go:114: INFO: Disconnected from relay relay://212.47.253.154:22067
	[SHORT] 2020/06/15 14:34:25.542315 model.go:1338: INFO: Connection to WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:52176-[2a01:e0a:WIN:101:IP:v6]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: reading length: read tcp [2a01:e0a:My::IP:v6]:52176->[2a01:e0a:WIN:101:IP:v6]:22010: use of closed network connection
	[SHORT] 2020/06/15 14:34:25.543035 model.go:1338: INFO: Connection to WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:42138-192.168.0.15:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256 closed: reading length: read tcp 192.168.0.49:42138->192.168.0.15:22015: use of closed network connection
	[SHORT] 2020/06/15 14:34:25.543589 model.go:1338: INFO: Connection to WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:53614-[2a01:e0a:WIN:103:IP:v6:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: Syncthing is being stopped
	[SHORT] 2020/06/15 14:34:25.544796 model.go:1338: INFO: Connection to REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:33602-RemoteIPv4:22290/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: reading length: read tcp4 192.168.0.49:33602->RemoteIPv4:22290: use of closed network connection
	[SHORT] 2020/06/15 14:34:25.727631 tcp_listen.go:89: INFO: TCP listener (0.0.0.0:32571) shutting down
	[SHORT] 2020/06/15 14:34:25.728602 syncthing.go:394: INFO: Exiting
	...
	Restarted with static lease, same IP

	[start] 2020/06/15 14:37:48.301162 main.go:588: INFO: syncthing v1.6.1 "Fermium Flea" (go1.14.4 linux-arm) deb@build.syncthing.net 2020-06-02 09:49:22 UTC
	[SHORT] 2020/06/15 14:37:48.497313 syncthing.go:159: INFO: My ID: SHORT-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH
	[SHORT] 2020/06/15 14:37:49.432711 sha256.go:87: INFO: Single thread SHA256 performance is 45 MB/s using crypto/sha256 (45 MB/s using minio/sha256-simd).
	[SHORT] 2020/06/15 14:37:50.099304 syncthing.go:191: INFO: Hashing performance is 41.14 MB/s
	[SHORT] 2020/06/15 14:37:50.099911 limiter.go:165: INFO: Overall send rate is unlimited, receive rate is unlimited
	[SHORT] 2020/06/15 14:37:50.100146 syncthing.go:289: INFO: Using discovery server https://discovery.syncthing.net/v2/?noannounce&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
	[SHORT] 2020/06/15 14:37:50.100259 relay_listen.go:63: INFO: Relay listener (dynamic+https://relays.syncthing.net/endpoint) starting
	[SHORT] 2020/06/15 14:37:50.100300 syncthing.go:289: INFO: Using discovery server https://discovery-v4.syncthing.net/v2/?nolookup&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
	[SHORT] 2020/06/15 14:37:50.100573 tcp_listen.go:62: INFO: TCP listener (0.0.0.0:32571) starting
	[SHORT] 2020/06/15 14:37:50.101213 model.go:366: INFO: Ready to synchronize "Folder1" (Folder1-ID) (receiveonly)
	[SHORT] 2020/06/15 14:37:50.102371 model.go:366: INFO: Ready to synchronize "Folder2" (Folder2-ID) (sendreceive)
	[SHORT] 2020/06/15 14:37:50.107643 folder.go:689: INFO: Completed initial scan of sendreceive folder "Folder2" (Folder2-ID)
	[SHORT] 2020/06/15 14:37:50.465830 syncthing.go:289: INFO: Using discovery server https://discovery-v6.syncthing.net/v2/?nolookup&id=LYXKCHX-VI3NYZR-ALCJBHF-WMZYSPK-QG6QJA3-MPFYMSO-U56GTUK-NA2MIAW
	[SHORT] 2020/06/15 14:37:50.655739 api.go:363: INFO: GUI and API listening on 127.0.0.1:8384
	[SHORT] 2020/06/15 14:37:50.655807 api.go:364: INFO: Access the GUI via the following URL: https://127.0.0.1:8384/
	[SHORT] 2020/06/15 14:37:50.655931 syncthing.go:350: INFO: My name is "Raspi"
	[SHORT] 2020/06/15 14:37:50.655988 syncthing.go:353: INFO: Device WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN101" at [dynamic]
	[SHORT] 2020/06/15 14:37:50.656024 syncthing.go:353: INFO: Device WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN102" at [dynamic]
	[SHORT] 2020/06/15 14:37:50.656058 syncthing.go:353: INFO: Device WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "WIN103" at [dynamic]
	[SHORT] 2020/06/15 14:37:50.656092 syncthing.go:353: INFO: Device REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH is "Remote" at [dynamic]
	[SHORT] 2020/06/15 14:37:50.853738 folder.go:689: INFO: Completed initial scan of receiveonly folder "Folder1" (Folder1-ID)
	[SHORT] 2020/06/15 14:37:50.945987 service.go:326: INFO: Established secure connection to WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:38214-[2a01:e0a:WIN:101:IP:v6]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:37:50.946209 model.go:1788: INFO: Device WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN101" at [2a01:e0a:My::IP:v6]:38214-[2a01:e0a:WIN:101:IP:v6]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:37:51.130109 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:37:51.130502 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:37:51.130729 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:37:51.130965 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:37:51.131304 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:37:51.131521 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:37:52.223756 service.go:326: INFO: Established secure connection to WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:51076-[2a01:e0a:WIN:102:IP:v6]:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256
	[SHORT] 2020/06/15 14:37:52.224047 model.go:1788: INFO: Device WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN102" at [2a01:e0a:My::IP:v6]:51076-[2a01:e0a:WIN:102:IP:v6]:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256
	[SHORT] 2020/06/15 14:37:52.530241 service.go:326: INFO: Established secure connection to WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:60260-192.168.0.20:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:37:52.530377 model.go:1788: INFO: Device WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.6.1" named "WIN103" at 192.168.0.49:60260-192.168.0.20:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:37:53.190007 service.go:326: INFO: Established secure connection to REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:47906-RemoteIPv4:22290/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:37:53.190123 model.go:1788: INFO: Device REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH client is "syncthing v1.7.0-rc.1" named "Remote" at 192.168.0.49:47906-RemoteIPv4:22290/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256
	[SHORT] 2020/06/15 14:38:01.223211 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:38:01.255026 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:38:05.262676 service.go:67: INFO: Detected 1 NAT service
	[SHORT] 2020/06/15 14:38:19.716837 static.go:68: INFO: Joined relay relay://185.108.129.133:22067
	[SHORT] 2020/06/15 14:41:01.256552 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:41:01.256794 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:41:01.257107 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:41:01.257282 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:41:01.257448 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:41:01.257652 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:41:11.264671 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:41:11.264917 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:44:11.266108 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:44:11.267042 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:44:11.267433 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:44:11.267698 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:44:11.267950 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:44:11.268129 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:44:21.274866 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:44:21.275490 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:47:21.276964 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:47:21.277342 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:47:21.277910 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:47:21.278309 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:47:21.278543 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:47:21.279106 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:47:31.285276 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:47:31.285511 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:50:31.286648 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:50:31.286892 upnp.go:154: DEBUG: Starting discovery of device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:50:31.287546 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:50:31.287632 upnp.go:163: DEBUG: Sending search request for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:50:31.287745 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0
	[SHORT] 2020/06/15 14:50:31.287838 upnp.go:173: DEBUG: Listening for UPnP response for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0
	[SHORT] 2020/06/15 14:50:41.294862 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:2 on eth0 finished.
	[SHORT] 2020/06/15 14:50:41.296100 upnp.go:219: DEBUG: Discovery for device type urn:schemas-upnp-org:device:InternetGatewayDevice:1 on eth0 finished.
	[SHORT] 2020/06/15 14:51:07.508686 tcp_listen.go:55: INFO: Listen (BEP/tcp): listen tcp :32571: bind: address already in use
	[SHORT] 2020/06/15 14:51:07.508841 service.go:139: INFO: c.S.listenerSupervisor: Failed service 'tcp://:32571' (1.000000 failures of 2.000000), restarting: true, error: "{tcp://:32571 tcp://:32571} returned unexpectedly", stacktrace: [unknown stack trace]
	[SHORT] 2020/06/15 14:51:07.508993 tcp_listen.go:55: INFO: Listen (BEP/tcp): listen tcp :32571: bind: address already in use
	[SHORT] 2020/06/15 14:51:07.509118 service.go:139: INFO: c.S.listenerSupervisor: Failed service 'tcp://:32571' (1.999994 failures of 2.000000), restarting: true, error: "{tcp://:32571 tcp://:32571} returned unexpectedly", stacktrace: [unknown stack trace]
	[SHORT] 2020/06/15 14:51:07.509326 tcp_listen.go:55: INFO: Listen (BEP/tcp): listen tcp :32571: bind: address already in use
	[SHORT] 2020/06/15 14:51:07.509418 service.go:167: INFO: Entering the backoff state.
	[SHORT] 2020/06/15 14:51:07.509545 service.go:139: INFO: c.S.listenerSupervisor: Failed service 'tcp://:32571' (2.999979 failures of 2.000000), restarting: false, error: "{tcp://:32571 tcp://:32571} returned unexpectedly", stacktrace: [unknown stack trace]
	[SHORT] 2020/06/15 14:51:08.327675 tcp_listen.go:89: INFO: TCP listener (0.0.0.0:32571) shutting down
	[SHORT] 2020/06/15 14:52:07.297795 model.go:1338: INFO: Connection to REMOTE-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:47906-RemoteIPv4:22290/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: reading length: read tcp4 192.168.0.49:47906->RemoteIPv4:22290: use of closed network connection
	[SHORT] 2020/06/15 14:52:07.297853 relay_listen.go:123: INFO: Relay listener (dynamic+https://relays.syncthing.net/endpoint) shutting down
	[SHORT] 2020/06/15 14:52:07.297973 static.go:114: INFO: Disconnected from relay relay://185.108.129.133:22067
	[SHORT] 2020/06/15 14:52:07.298277 model.go:1338: INFO: Connection to WIN101-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:38214-[2a01:e0a:WIN:101:IP:v6]:22010/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: Syncthing is being stopped
	[SHORT] 2020/06/15 14:52:07.298451 model.go:1338: INFO: Connection to WIN102-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at [2a01:e0a:My::IP:v6]:51076-[2a01:e0a:WIN:102:IP:v6]:22015/tcp-client/TLS1.3-TLS_CHACHA20_POLY1305_SHA256 closed: reading length: read tcp [2a01:e0a:My::IP:v6]:51076->[2a01:e0a:WIN:102:IP:v6]:22015: use of closed network connection
	[SHORT] 2020/06/15 14:52:07.298698 model.go:1338: INFO: Connection to WIN103-BBBBBBB-CCCCCCC-DDDDDDD-EEEEEEE-FFFFFFF-GGGGGGG-HHHHHHH at 192.168.0.49:60260-192.168.0.20:22020/tcp-client/TLS1.3-TLS_AES_128_GCM_SHA256 closed: Syncthing is being stopped
	[SHORT] 2020/06/15 14:52:07.299646 syncthing.go:394: INFO: Exiting

Your firewall/network configuration is not allowing broadcasts/multicasts, so it’s not finding anything. The “1 device found” reported is NATPnP which does not have a real discovery mechanism, so it’s always “discovered” and just fails when adding a port mapping if its not supported or not there.

Thank you Audrius, sorry it took so long to reply. So you’re right, I only added allow ingress/port-forward for ssh & syncthing into both firewall and NAT router. You say NATPnP, I don’t find this on the Internet, instead I find NAT-PMP, UPNP et PCP. I guess Syncthing has it’s own punch-hole mechanism embedded, but I couldn’t be able to find which (the credits refer to jackpal & your own fork but I’m not sure). Whatever although I had default allow all out policy plus these default ingress rules that seem to allow upnp:

Chain INPUT (policy DROP)
target     prot opt in     out     source               destination
ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            ctstate RELATED,ESTABLISHED
DROP       all  --  *      *       0.0.0.0/0            0.0.0.0/0            ctstate INVALID
... #ACCEPT dhcp & icmp subset
    SubChain ufw-not-local
    target     prot opt in     out     source               destination
    RETURN     all  --  *      *       0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type LOCAL
    RETURN     all  --  *      *       0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type MULTICAST
    RETURN     all  --  *      *       0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type BROADCAST
    ufw-logging-deny all  --  *      *       0.0.0.0/0            0.0.0.0/0            limit: avg 3/min burst 10
    DROP       all  --  *      *       0.0.0.0/0            0.0.0.0/0
Chain INPUT (policy DROP)(continued)
target     prot opt in     out     source               destination
ACCEPT     udp  --  *      *       0.0.0.0/0            224.0.0.251          udp dpt:5353
ACCEPT     udp  --  *      *       0.0.0.0/0            239.255.255.250      udp dpt:1900

…both my syncthing and sshd dynamic port-forwards were magically created only when I added this rule in the end:

ACCEPT     udp  --  *      *       192.168.0.0/16            0.0.0.0/0      udp spt:1900

Yes you read well: spt, source port. The best is that there is 2 different upnp instances in the raspberry: syncthing if IUC, plus miniupnpc I use this way from a cronjob:

0/15 * * * * a=`hostname -I|cut -d" " -f1` && upnpc -a $a -e ssh2pi 15222 21522 TCP 3600

The custom rule, although I feel it suspicious (but I’m not confident), resolved the 2 issues at once, syncthing portfw not being created and miniupnpc moaning “No IGD UPnP Device found on the network !”. For Syncthing this was not a real big problem because I have control over the router on the other side so even the link won’t need to fall back using the relays poor workaround, I know I won’t need this with help of discovery servers. Starting syncthing with STTRACE=upnp along with firewall full log helped me to discover which packets got lost (the one beginning with 3 “*” in the FW log excerpt below):

...:34 [84490.315607] [UFW AUDIT] IN= OUT=lo SRC=0000:0000:0000:0000:0000:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 PROTO=ICMPv6 TYPE=143 CODE=0 
...:34 [84490.315686] [UFW AUDIT] IN=lo OUT= MAC=00:00:00:00:00:00:00:00:00:00:00:00:86:dd SRC=0000:0000:0000:0000:0000:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0016 LEN=76 TC=0 HOPLIMIT=1 FLOWLBL=0 PROTO=ICMPv6 TYPE=143 CODE=0 
...
...:34 [84490.340487] [UFW AUDIT] IN= OUT=eth0 SRC=RAS.PI.LAN.V4 DST=GAT.WAY.LAN.V4 LEN=30 TOS=0x00 PREC=0x00 TTL=64 ID=24593 DF PROTO=UDP SPT=54385 DPT=5351 LEN=10 
...:34 [84490.340504] [UFW ALLOW] IN= OUT=eth0 SRC=192.168.00.49 DST=192.168.00.254 LEN=30 TOS=0x00 PREC=0x00 TTL=64 ID=24593 DF PROTO=UDP SPT=54385 DPT=5351 LEN=10 
...:34 [84490.340793] [UFW AUDIT] IN=eth0 OUT= MAC=RA:SP:IM:AC:AD:DR:GA:TW:YM:AC:AD:DR:08:00 SRC=192.168.0.254 DST=192.168.0.49 LEN=58 TOS=0x00 PREC=0xC0 TTL=64 ID=28201 PROTO=ICMP TYPE=3 CODE=3 [SRC=192.168.0.49 DST=192.168.0.254 LEN=30 TOS=0x00 PREC=0x00 TTL=64 ID=24593 DF PROTO=UDP SPT=54385 DPT=5351 LEN=10 ] 
...
...:34 [84490.341359] [UFW AUDIT] IN= OUT=eth0 SRC=192.168.0.49 DST=239.255.255.250 LEN=195 TOS=0x00 PREC=0x00 TTL=1 ID=470 DF PROTO=UDP SPT=47644 DPT=1900 LEN=175 
...:34 [84490.341373] [UFW ALLOW] IN= OUT=eth0 SRC=192.168.0.49 DST=239.255.255.250 LEN=195 TOS=0x00 PREC=0x00 TTL=1 ID=470 DF PROTO=UDP SPT=47644 DPT=1900 LEN=175 
...
...:34 [84490.341966] [UFW AUDIT] IN= OUT=eth0 SRC=192.168.0.49 DST=239.255.255.250 LEN=195 TOS=0x00 PREC=0x00 TTL=1 ID=471 DF PROTO=UDP SPT=42597 DPT=1900 LEN=175 
...
...:34 [84490.341980] [UFW ALLOW] IN= OUT=eth0 SRC=192.168.0.49 DST=239.255.255.250 LEN=195 TOS=0x00 PREC=0x00 TTL=1 ID=471 DF PROTO=UDP SPT=42597 DPT=1900 LEN=175 
...
***:34 [84490.342324] [UFW AUDIT] IN=eth0 OUT= MAC=RA:SP:IM:AC:AD:DR:GA:TW:YM:AC:AD:DR:08:00 SRC=192.168.0.254 DST=192.168.0.49 LEN=330 TOS=0x00 PREC=0x00 TTL=64 ID=33909 DF PROTO=UDP SPT=1900 DPT=47644 LEN=310 
...:34 [84490.365550] [UFW AUDIT] IN= OUT=eth0 SRC=192.168.0.49 DST=224.0.0.22 LEN=40 TOS=0x00 PREC=0xC0 TTL=1 ID=0 DF PROTO=2 MARK=0x114 
...:34 [84490.365570] [UFW ALLOW] IN= OUT=eth0 SRC=192.168.0.49 DST=224.0.0.22 LEN=40 TOS=0x00 PREC=0xC0 TTL=1 ID=0 DF PROTO=2 MARK=0x114 
...
...:34 [84490.422317] [UFW AUDIT] IN= OUT=eth0 SRC=192.168.0.49 DST=192.168.0.254 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=60125 DF PROTO=TCP SPT=49874 DPT=5678 WINDOW=29200 RES=0x00 SYN URGP=0 
...:34 [84490.422336] [UFW ALLOW] IN= OUT=eth0 SRC=192.168.0.49 DST=192.168.0.254 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=60125 DF PROTO=TCP SPT=49874 DPT=5678 WINDOW=29200 RES=0x00 SYN URGP=0 
...:34 [84490.422660] [UFW AUDIT] IN=eth0 OUT= MAC=RA:SP:IM:AC:AD:DR:GA:TW:YM:AC:AD:DR:08:00 SRC=192.168.0.254 DST=192.168.0.49 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=TCP SPT=5678 DPT=49874 WINDOW=28960 RES=0x00 ACK SYN URGP=0 
...:34 [84490.422696] [UFW AUDIT] IN= OUT=eth0 SRC=192.168.0.49 DST=192.168.0.254 LEN=52 TOS=0x00 PREC=0x00 TTL=64 ID=60126 DF PROTO=TCP SPT=49874 DPT=5678 WINDOW=229 RES=0x00 ACK URGP=0 

Although multicast ingress was allowed as a whole, it seem it was not enough IUC and maybe there is a bug in the default rules of this UFW firewall for newby users.