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
FWIW, this worked for me. Some of the steps might need to be more prescriptive for folks not very familiar with Macs, but I got it working in one pass. If you want a different drive name than "Macintosh HD" you will need to edit the global constant lines of Autobypass-mdm.sh to reflect the drive name you want.
I did have to connect to the internet to activate as well, but as soon as I hit the "This device is owned by an organization" page, I hit COMMAND-Q, booted in to Recovery Mode, then picked up the instructions from there and ran the script.