Same issue. Devastating to workflow for the past week. I have multiple user accounts. Mine is an administrator account. Have run disk utility First Aid on all available volumes, then reinstalled Big Sur OSX V. 11.3.1. On restart and login, Finder fails to load, and iMac is unbearably slow. Went into Safe Mode and created new admin user. Finder opens quickly and IMac runs like a top, but of course, all the stuff I need is under my original admin user, so I restart and log in under the original admin user and again, no Finder, iMac exceedingly slow. Ready to tear out my hair. Apple, anytime you want to jump in this thread to help out, feel free. I am going to have some very ****** off clients soon!