Had the same issue with a 2017 iMac Pro, random restarts running Big Sur 11.1 same crash logs as everyone else on this thread. Thought it might be related to running two extra monitors off the iMac, however I can't understand why it was fine for weeks and then started to crash for last couple of days. Whilst I don't have good news relating to some software fix, I can report that I successfully wiped the drive, fresh installed Catalina and the best news, was able to restore my Big Sur backup from earlier today. This downgrade was not possible to do previous to Big Sur. So either Apple foresaw the need to allow restoring a time machine backup to an earlier Mac OS due to the newness of Big Sur or I've had some miracle performed and should buy a lotto ticket before my luck runs out. So just keep in mind there may be a downgrade path for you using Time Machine and this definitely was not possible to perform with the last few releases of Mac OS. Hope that helps.