I was wondering if Spotify's Discover Weekly playlist can see what you play with other apps, or if it just takes into account t what you listen to on the Spotify service only. I use Tidal primarily for listening, but I still use Spotify a little. Just curious. Maybe last.FM scrobbles?
Discover Weekly only uses data aggregated withing Spotify itself. Last.FM scrobbles won't influence your Discover Weekly playlist. If you want to, you can read more about the data used for personal playlists within Spotify here.