The solution looks like navigating to ~/Library/Mobile Documents and deleting the entire folder. It shouldn't cause you any problems, because you don't use iCloud.
As long as you're satisfied that you've got no relationship with iCloud/iCloud drive, trashing the folder will be a harmless procedure.
MacBook Pro - M2, Ventura 13.6 Safari Tech Prev 17.0 Safari 16.6 Firefox 116.0.2 iPhone 7 Version 15.8
