mac big sur could not load preferences pane

For sure, it is a bit extreme measure.

Try startup in Safe Mode.

Startup in Safe mode. https://support.apple.com/en-gb/HT201262

To leave Safe Mode, click  in the menu bar and choose “Restart”

Quote:

Safe mode prevents your Mac from loading certain software when it starts up, including login items, system extensions not required by macOS, and fonts not installed by macOS. It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. And it deletes some system caches, including font caches and the kernel cache, which will be created again automatically as needed.

Scott Stark wrote:

After upgrading to big sur I get this message when trying to open system preferences: mac big sur could not load preferences panemac big sur could not load preferences pane".

How to fix? thanks.

If Screen Time is on, this could restrict access to System Preferences on the Mac. Here is an article to follow on steps to help resolve this issue:

Use Screen Time on your Mac

ref: https://discussions.apple.com/thread/251700483?answerId=253279227022#253279227022

Try reinstalling macOS. after backing up.

https://support.apple.com/en-us/HT204904