Mac Mini M2 Pro with the same issue. All of my other Macs (another Mac Mini M2 Pro, Mac Mini M2 and Mac Studio M2 Max) have all updated just fine. Getting same error as OP. I've turned off beta updates, rebooted a million times and same issue each time.
fightingmajor
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Same error on a 2020 Mac mini. I have Big Sur installed on an external hd that I boot to.