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
Can confirm this works, I didn't update at all since 14, since last november and also didn't see minor updates like 14.2 or14.3 and so on, but recently saw 15.1 and just updated now and so far looks good
I prev did skipmdm steps and etc file changes but thats about it
I'll update if things change but your comment really gave me the courage to update directly, so thank you :)