Background:
I use VNC alot.
I VNC to a lot of my other machines (VNC viewer).
That is on THIS machine.
I want to try some new software and didn't want to do it on THIS machine. I have another NUC (Ubuntu) and so I thought I would use it. It was running 18.04 and a lot of other OLD software which I needed to update too.
So I though I would bring it up to date then update the other software. That was a long journey, but it worked.
Other software updated.
Looking great.
But I couldn't VNC to it.
Bit of digging:
Wayland and VNC are NOT COMPATIBLE!
Which is probably why I don't have it on THIS machine.
Annoying I wasn't asked if I wanted it or not when updating.
Found an article how to disable Wayland
1 file, 1 line. Edit that line, remove the #
.
Did it.
Rebooted.
System error, contact sysadmin.
Help. I'm guessing I need a USB-BOOT (with a version of Ubuntu) on it, boot, log into the SSD in the NUC, edit the file, then reboot.