@prologic@twtxt.net
I got it! syncthing 3 way synchronize without global announcement. Acces on LAN and via Tailscale VPN. Also Setting the NAS as introducer on the individual devices and the lan IP with port (e.g: tcp://10.0.0.10:22000) and the Tailscale IP with port. The port should be the one you expose out of the container which’s internally mapped to 22000. You set these IP instead of the dynamic entry in the advanced tab.

I can give you the docker-compose file tomorrow. I am
typing this on my phone right now and do not have the ability to copy such along text.