Just for information, I disabled Symmetric NAT (ticked “Static Port”) for the whole network NAT and not only for port 22000, and can see the following in the Synthing log:
2025-06-10 23:36:44 quic://0.0.0.0:22000 detected NAT type: Port restricted NAT
Did still not help, it keeps displaying “Disconnected”.
And then I enabled Port Forwarding for TCP/UDP 22000 and it looks a bit better:
Maybe your problem is with discovery, so that the other side simply doesn’t know where to try connecting?
Show a screenshot of the “This Device” section of the GUI. What do the Listeners and Discovery entries show? Please also show the dialog that opens when clicking on the “x/y” numbers.
Just to make this clear, you do need some patience, as Syncthing will make many connection attempts in turn, and it may take some time until the correct address is tried. Don’t expect anything to happen instantly.
Debug logging may help as well, to see where the other side is trying to connect and what the result is for each address tried. And what addresses it has discovered for the device behind your NAT.
Relay LAN is not possible at the moment. Relay connections are always considered WAN by Syncthing [1] [2]. If it was possible it would show up as Connection Type of “Relay LAN” with 2 bars in the GUI.
How not to love this? 
