A few weeks after upgrading to Big Sur I started having problems shutting down:
Roughly two out of three times the Mac hangs with an empty screen and spinning cursor for several minutes. Then it crashes with a kernel panic message and finally reboots taking me back to the login screen. It happens on both our Macs.
Quite a few others are seeing the same behaviour:
It seems that it’s caused by external drives – perhaps in particular those used by Time Machine – and some people have had success by formatting their drives as APFS.
I can confirm this. We have a Time Capsule that is formatted as HFS+. When we are away from the TC, the Macs shut down quickly without problems. I’m reluctant to reformat the TC as I would lose the backups, but it seems I have no other choice, or have I?