Couldn't see anything in the roadmap or anything, but this may be relevant: https://www.theverge.com/2020/3/24/21192473/spotify-revoking-support-developer-api-third-party-dj-apps-algoriddim-djay

MIXO is all about your music, it's not built to stream music from third party sources.

It also does look like Spotify are dropping third party integrations from July:

https://www.theverge.com/2020/3/24/21192473/spotify-revoking-support-developer-api-third-party-dj-apps-algoriddim-djay

Would love it if you can consider integrating Spotify Playlists into Mixo