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
At what point do you use the SkipMDM steps if you are turning on a MacBook for the first time which is marked for JAMF activation/enrolment during initial setup?
Is disabling WIFI router still a workaround to get you into the OS / restore from a backup and then run the SkipMDM script?