Airsonic: https://github.com/airsonic/airsonic

Airsonic (like Subsonic before it) lets me have the best of both worlds by automatically transcoding my FLAC library to VBR MP3 on the fly when I stream music to my phone over LTE. It's a Java webapp (.war), and the standalone exe version just bundles (iirc) Jetty. I run it in Tomcat9 just as well.

My client recommendations are play:Sub on iOS and DSub on Android: https://apps.apple.com/us/app/play-sub-music-streamer/id9553... https://play.google.com/store/apps/details?id=github.daneren...

Funkwhale for the backend and Otter for the mobile front end. https://funkwhale.audio/en_US/ https://github.com/apognu/otter

Navidrome is a recent in the scene of alternatives. I had been running Airsonic on a Pi for about 2yrs now, and recently started to test Navidrome. It is lighter on my Pi than Airsonic and also has a refreshing UI. Since Navidrome uses Subsonic apis, any app that supports Subsonic/Airsonic will support Navidrome too.

I use AssetUPnP to serve music off my NAS (my collection is largely classical and has may more relevant tags than most UPnP servers handle). I have a Naim amp that understands UPnP, or BubbleUPnP on my phone.

Plex? They just released a new update to there dedicated music player app which is pretty good.

Plex is pretty good for music now