Photos app hangs when synchronizing with iCloud
The Photos app on my Mac stopped synchronizing with ICloud a few weeks ago. That was still on Catalina. I have now upgraded to Big Sur, but no change with the Photos problem.
I tried a couple of things already, like disabling and re-enabling Notes syncing, restarting the Mac, logging out of iCLoud alltogether, and then logging in again. No avail. The syncing hangs at "Uploading 6,954 Items". Internet connectivity is fast.
This problem seems to show up in support forums in multiple variations, but I haven't seen a any systematic checklist or process to reset Photos and the sync process. Apple Support didn't help.
MacBook Pro 13″, macOS 11.0