For playback (ie, self host your own streaming service), you want Airsonic or Navidrome, with any Subsonic compatible app on your devices.

You can also go Jellyfin with Finamp, but it’s a video service first, whereas the others are much more audio focused.

For audiobooks and podcasts, Audiobookshelf. It has its own app.

For downloading music, you want Lidarr or Headphones. Fair warning, the music torrenting scene really died off with Spotify, so you’ll probably want to get on some Usenet groups to have good sources for the releases you want.

If you want to add audiobooks, Readarr can apparently handle that.