Ahhh i gotcha, so basically it forwards traffic through the pi so that you can send traffic through tailscale on devices that don’t support it? Sounds like a cool idea tbh
Good on ya for the tailscale/syncthing though, off-site backups are super important! If Jellyfin supported federation you could merge your library and your parents library and have it all accessible through each of your local instances. Maybe one day they’ll add it, i think it would be a killer feature.
Glad the write-up helped though, it should at least help you move towards single instances (at least for immich) since you can just backup on tailscale via the dns entry!
Once the port is open, you should be able to access it via the tailscale IP just as you would locally on your network