csrutil disable
Restart computer
In the terminal, type
sudo open /Applications/TextEdit.app /System/Library/LaunchDaemons/com.apple.ManagedClient.enroll.plist
change
<key>com.apple.ManagedClient.enroll</key>
<true/>
to
<key>com.apple.ManagedClient.enroll</key>
<false/>
So that the changes take effect
The previous work arounds have been tested; if they didn’t work, some step was not followed or completed. In Sam’s case I think the only extra thing I did was close/dismiss the notification and they never came back. Paul since you already have an email address for me, you can reach me there; but the same info or reply I said last time still applies.
As for bypassing the password; yes you can reset passwords without losing data as long as encryption (FileVault) was used. A google search for Mac password reset can get you to Apples support site with instructions. If the storage device is removable, it can be attached to another computer that can read the file system (another Mac) and the data can be accessed (as long as encryption was not used).
If encryption was used, then you are out of luck without a password or recovery key. A recovery key would have to be manually recorded or stored in iCloud with the users AppleID. In extreme cases (for large governments with lots of $), it can be possible to brute force a simple short password or a password where there are clues to what the password is.