I don't know anything about this technology but it seems like a really cool idea to share the stems for an entire album to play around with. Maybe someone here with some mixing talent could take a stab at a surround mix (assuming this actually allows you to do that)? For anyone not familiar with Umphrey's McGee, they are a talented prog/jam band, who improvise with the best them when playing live.
https://myxstem.com/asking-for-a-friend/
https://myxstem.com/asking-for-a-friend/