Ok, I tried it and it worked and didn't have to turn off activation lock. I was able to reinstall the Catalina but while I was updating to Big Sur, in the midst of the installation, I got a message saying that the computer had the restart because of a problem. Let's see it this continues. If it does, then it certainly must be Big Sur for some strange reason not liking my computer.I would hope so.
Your problem can also be caused by Activation lock and if that's on you'll need to take your Mac off iCloud as per that link (with another Apple device). Hopefully not on.