Wow. I can't believe such an egregious bug (or, worse yet, default behavior) made it to a Gold Master, let alone a release candidate.
I've tried turning off iCloud Drive, then quitting OneDrive, Google Drive and Dropbox, then force-quitting anything with “cloud” in its name, then booting into safe mode and logging in into an Admin account with nothing on it. NOTHING WORKS.
I'm going to try and log out of iCloud in this and on my main account and try again.
I've been a Mac user since 2003; my iMac G4 came with Jaguar pre-installed and Panther CD install media (yeah, *that's* how old it was). My iMac G5 came with Panther, and I actually bought Tiger and then got Leopard through, err, other means, and have since been using Time Machine. It NEVER failed me in EIGHTEEN years. Apple's internal testing and QC is really going down the drain. It's beyond ridiculous that what reviewers have been widely calling a “minor release” could come out with such stupid bugs… Clearly they've been messing stuff up under the hood and didn't tell anyone about it. Had I known about this, and I'd have waited until 14.2, 14.3…
Also, what sense does it even make for Time Machine not to attempt even an incomplete backup because of some cloud files? They're in the cloud or can be backed up over there at any moment, for crying out loud…
Suffice to say, I already have a little call with Apple Support scheduled for tomorrow morning. For their own sake, I hope I can fix the issue until then.
Oh, and while writing this comment, I'm getting strings of text from a few lines up flashing on top of the current line. This is bizarre, Safari seems to be completely FUBARed. I should be making a screen recording of this. Yikes!