Get all spotify playlists (for all users)

[yardo3]

I'm trying to build an app that will show with song appears frequently along with other songs in a playlist.

In order to do this I need to find all the playlists containing a specific song, but I didn't find an API for this. According to this Reddit comment this API should exist, or used to.

One alternative approach could be to download/cache all playlists for ALL users and check manually if the song is contained in any of those playlists, but the only API I saw was the one to get all the playlists for a specific user.

Another alternative approach could be to get the list of ALL users and then download the playlists for each one of them, but I also didn't find a way to get a list of all usernames.

Is any of these a viable approach? Does any of these APIs exist?