It should just work if you don’t have any specific run conditions enabled. I don’t think they will be able to discover each other locally as I suspect tethering does not establish a lan, even if it does, I suspect broadcasts will be disabled, so it will either connect via external ips or even relays.
When I disabled Wifi, enable USB tethering and having no mobile internet (real use case: I travel by train to my work and have no mobile connection for about 30 minutes) I get an error message by Syncthing: ‘No network connection or airplane mode enabled’.
While writing this message, I discovered the ‘Run when device is in flight mode’ option. Maybe this solves my problem .
Yeah if you’ve no connection to the outside world you need to configure your run-conditions in the Android wrapper, otherwise it won’t start. Any issues other than that?
(Offtopic, but thanks @calmh for the forum update. Editing works again.)