I also had this problem using Xcode 12.4. Following other suggestions here, I deleted my real devices from Xcode. That alone didn't fix it. But as others here have suggested, I re-added my devices and set them up as they had been set up before. And that worked. No more beach balls.

If your info.plist has a key for Privacy - Music Usage Description you need to remove it.

It likely does apply to what you're trying to do. If you're looking to play sections of songs that is synced to any other media, such as video or at a certain point in a game, this requires a different license than music streaming. It would require a sychronization license - https://en.wikipedia.org/wiki/Synchronization_rights.

App Store Review Guidelines - Section 4.5.2 covers Apple Music - https://developer.apple.com/app-store/review/guidelines/