Music support exists but needs a lot of love. Currently for my usecase (streaming my music to my Android phone) transcoding doesn't currently work (streaming flac over a mobile data connection is bad news) so I've fallen back to using dsub/gonic (subsonic compatible server) until transcoding is resolved.
It finds metadata pretty well (Artwork, artist info, and summaries) but playback leaves a fair bit to be desired and playlists aren't very well fleshed out.
Personally I'm just not a huge fan of java and the web interface was a bit on the annoying side, although it has a few more features like grabbing podcasts (which never really seemed to be implemented into other clients).
As far as gonic goes I've been testing it out for a while and haven't run into any issues and I'm a bit of a fanboy for stuff made in go. It's still pretty bare-bones, but has been pretty stable and fast otherwise.
Looking into it would seem that gonic might not actually do transcoding yet (airsonic could transcode into opus after some configuration which is nice) although, caching from dsub might have saved me there if that's the case.
The main issue with jellyfin as far as mobile stuff goes is that it doesn't cache any tracks so if I was going between wifi signals audio would frequently cut out which was never a problem with airsonic/gonic as dsub will request a couple of tracks ahead of time to compensate for deadzones.
