Is the main use case here to stream from your own library like a plex for music? Or something else?

I’m not sure what you mean by connect different sources, I generally just use Spotify so maybe I’m not the ideal user here. I’d definitely see value in transitioning off of Spotify but that would require me to keep my own library of music and while I’m sure a sonar/radar pipeline exists for this I’d find it limiting for finding new music. Spotify’s discover weekly and playlists of stuff I’ve never heard before keep me hooked.