I think I fixed it, but I don't know exactly what part did the trick: reboot into recovery first aid on system-disks setting startup security to high restarted into Big Sur and Update runs without any error

I think I fixed it, but I don't know exactly what part did the trick: reboot into recovery first aid on system-disks setting startup security to high restarted into Big Sur and Update runs without any error

I think I fixed it, but I don't know exactly what part did the trick: reboot into recovery first help on system-disks setting startup security to high restarted into Big Sur and Update runs without any error