

You might be interested in Tapesonic then (a shameless plug). Streaming YouTube stuff is borked though (needs newer yt-dlp - you can try rebuilding the container yourself with a new alpine version); also grabbing non-library tracks is not supported for ListenBrainz for now (their API doesn’t return the URLs, I’ll work around this in the future; meanwhile you can still get the playlists of the stuff you already have in your library).
Seeing the recommendations in your Subsonic player (even the ones you don’t have in your library) currently works with last.fm auto-generated “playlists” (stations, as they call them). Streaming them is broken but easily fixable, I just haven’t gotten around to it.
YouTube links in the player would probably need updates to the OpenSubsonic specification and support on clients/servers - but I don’t really see why someone would want this if you could just stream those without leaving the player.
I’m working on a big update (multi-user support which required reworking almost everything, haha…) that’s been blocking me from doing basically anything else. After that goes live somewhere around January-February (along with updated yt-dlp which will fix streaming stuff from YouTube) one of the priorities will be implementing Bandcamp auto-search. This will allow better matching for last.fm recommendations and also matching non-library tracks for ListenBrainz.