I've started work on a tool that I envision will allow users to easily convert links from one music streaming service to another. The reason for it's existence is I was tired of opening Spotify to search a link to a song I'm trying to show someone, since nobody I know uses YouTube Music, and I really don't want to use Spotify.
Right now it only supports converting Youtube Music links to Spotify, as that is my use case, but the framework is there for other streaming platforms that expose APIs. I made it because I'm envisioning a tool built on top of it that can port playlists between services, perhaps even in real time - so that collaborative playlists across platforms becomes possible.
The biggest challenge I'm facing right now is the fact that YouTube Music does not have any public API at all as far as I can tell, limiting me to the YouTube Data API, which is not ideal. Spotify seems to have a lovely API though!
It's very early stages, but if the idea interests you, let me know what you think!
https://github.com/kn100/conjugate/