You said there’s no other option, I just listed some options. Also Funkwhale is decentralised, there’s no corporation backing it. Ofc, you can also just download the music you like.
With xManager, the free tier comes quite close to premium. No ads, play whatever music you like. The only issues are lower sound quality & no downloads, which are really non-issues since you can just find other sources to download the music from, at flac quality
Personally, I feel the same way you do about DRM. If you’ve paid to own it, then it should be owned outright. With this in mind, I would say pirating them wouldn’t lose you any moral ground.
It lacks some of the functions found in plex, most notably the sync feature. That being said, it’s still a very good free alternative to plex. It does run on android tv