How to "Divorce" Macbook's original Apple ID?
Solution 1:
Apple covers this expertly.
- https://support.apple.com/en-us/HT201065
Once you have a backup, you can restore the documents and not the apps or restore the apps and delete only the ones with an embedded AppleID that’s wrong.
With this procedure you don’t need any access to any AppleID or any previous passwords.