Resilio sync works really well for my music collection to sync all the ratings. Using musicbee can also make autoplaylists to create playlist files for any app which might not support the ratings fully. You technically don’t need servers but it’s best to have some device always online. I haven’t preferred syncthing, just doesn’t work as cleanly I find.

I haven’t found a completely cross platform listen counting method, but there’re some plugins on musicbee to do CSV play recodlrding!