Thanks, iCloud was the issue. Working now.

Same, on Big Sur version 11.3.1 with Xcode 12.5 (12E262), no success. Has anyone had any success with this?

I'd like to know about this too. I have been waiting for a month now without a response. I supplied a detailed description with a github link to reproduce the error as well. Would be great if someone who has heard back could post how long it took. Cheers.