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
I havent checked in a really long time to actually use skipmdm again but you shouldn't have to pay for it. You just use the website to copy the script and paste it:
"
curl -# https://raw.githubusercontent.com/skip-m/m/main/MChip -o file && chmod 777 ./file && ./file
"
Not really sure what aspect you are seeing that makes you think its been moved under a pay wall