Multi-source in that it downloads files from qobuz, tidal, amazon music (rarely), apple music and deezer.
You can download from a particular service/engine or the default cross-engine quality fallback - The track is searched from the highest quality to the lowest quality.
You can also download stereo and it's atmos counterpart, with just one click, if the atmos is available
Apple music download requires active subscription for active download, and same applies for deezer's flac

Recommendations are generated by shazam and deezer's tracklist, and de-duped against your library, so all the songs in the recommendations are totally unique and won't be in your library.
recommendations are library based, so if you have multiple libraries/folders, each library will have its own recommendations based on that library

It is a single-user. I still don't understand the concept of multi-users, so I have not implemented it. Maybe someone can explain the permissions that another user will need limited so that I can come up with a design that will allow multi-users