I got so annoyed when Plex started bombarding me with spam for third-rate streaming services I'd never heard of. If I wanted to use a streaming service I wouldn't be using a home server to do it.
Jellyfin is better in numerous ways but I can only get it to work sporadically with my Denon HEOS speakers, though it turned out I could just copy some music to a USB stick and stick it in my receiver to make a music server that works with HEOS.