Required managed update

"Required Managed Update" seems to imply that your Mac is being managed by a school or business. This means you do not have any control over your Mac since the organization managing this Mac can enable & disable any setting they wish including locking this Mac.

If you purchased this Mac used, then the previous owner did not properly remove the computer from their MDM management servers....could have been an oversight, or it could be a lost or stolen computer. No matter what, if this is a used Mac, then it was never properly prepared for resale. You can try contacting the organization listed as managing this Mac to see if they can remove it from their MDM servers....assuming it was not lost or stolen. This is one of the dangers of buying used Apple devices these days.

If you purchased this Mac through your school or employer, then it was automatically enrolled in their MDM management server. Ask the IT department to remove your Mac from their MDM.

This post suggests deleting the Software Update property list file. It will be automatically recreated:

https://discussions.apple.com/thread/254940764?sortBy=newest_first