I've used Gonic[1] for music server purposes and Symfonium[2] for streaming said music for a while now, nothing but good things to say about both. The only downside is it does not do automatic media tagging like Plex, but if you ingest with something like MusicBrainz Picard[3] then it'll never be a problem.

[1] https://github.com/sentriz/gonic [2] https://www.symfonium.app/ [3] https://picard.musicbrainz.org/