Time machine locks external drives
The current versions of Monterey deletes data on an external drive when the drive is selected as a back-up. See below.
After back up the disk was locked as Read only. See also below. No padlock to change access to the disk.
This is a new feature. I have been using external hard drives for manual storage offline and as a Time machine backup without issue.
I have a 4TB disk and want to use it for multiple purposes.