Now i am unsure where to answer, when in that thread you link i say fountain.fm is a sovereign spotify, i mean that in all it’s glory and gloom. While it allows you to put any feed in there as long as it is indexed by the podcastindex.org (hence why diskspace is delegated for audio/video data). (You can even push livestreams.) I’m not super interested in that particular app, because of the spotify side of it. The source is not open, and not even Dog knows how their recommendation bonanza works. They do the usual capitalist thing: put themselves in the middle. They can make all the promises in the world, nothing can concretely stop them from using that middle position to pivot into pure BS.
But it gives some cool ideas about what can be done.