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
@DaWallyLama glad to hear my notes worked. My Mac is still running strong to this day. I have not tried activating another Mac or iPad with the machine in question, but interesting to note. To @secured2k's point the newer Macs behave differently. I recently nuked an MDM loaded machine from my previous employer using these steps @peon666 https://graffino.com/til/UmkCdmEx7v-remove-a-non-removable-mdm-profile-from-macos-without-a-complete-wipe. YMMV but it worked for me on a 2019 intel Macbook pro.