Soulseek.
kandykarter
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'm in a similar boat, switched from Android TV clients to a couple little beelink N100 boxes (which are great). I use Kodi as my Jellyfin client which works great especially with a remote/from the couch, and a cursory search would imply that Kodi has plugins for Prime Video and Disney Plus, but I don't use those, so I have no first-hand experience.
The big one that annoys me right now is the lack of a TV interface for Spotify outside of the walled gardens of Android, Apple, and Roku. The desktop app does not play well with anything but mouse and keyboard.
Another thing to note is that Jellyfin Media Player plays really nicely on a TV/Remote control setup.
Check out Soularr, pretty new, scripts to integrate slskd and lidarr, works great for me paired with Deezer downloading through arr-scripts.