The workaround didn't work on the first attempt on mine - went through the whole process and booted back to the Oops screen, followed by frozen start up apps. Am waiting for further ideas from the Zorins.
PS The good news is that upgrade of 17 Core to 18 Core was successful on my laptop, though very slow on installing the upgrades (step 4).
Now back to 17 Pro to 18 Pro
