Soulseek.

Scott Thompson as Elizabeth II

I’ll echo what most people here are saying, Jellyfin (which is what I use) or something with the subsonic API, and Symfonium. It’s non-free, but it’s a cheap one-time payment and it’s genuinely an excellent mobile app.

As far as building your library, I do use Lidarr, but it’s a lot more hit-and-miss than Radarr or Sonarr are for their respective mediums. For music, much like back in the day, Soulseek is still the best option. In fact, you can selfhost slskd, which is a great modern web interface for it.

I do all my shoplifting and self-checkout fraud there. SUPER affordable.