So after installing Ubuntu 20.04 on a Dell Optiplex 5080, everything seemed fine, ran some updates and after reboot the machine just had a blinking cursor in the top left hand corner of the screen.
As I’d just set it up, I couldn’t be bothered troubleshooting, so I reformatted.
All working after a reformat, ran the updates, same result, blinking cursor in the top left corner.
Annoying.

So, with google at my fingertips, it wasn’t long before I found that rm -rf / was the solution!

OF COURSE I’M KIDDING

At the blinking cursor screen, you can get into the system by pressing CTRL ALT F2 (some machines may respond better to F1 or F3 in combination with CTRL ALT)
Log in with your credentials then

sudo nano /etc/default/grub

find the line with GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash” and add nomodeset so that it looks like

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"

Then update grub with

sudo update grub

and then reboot with

sudo reboot

You should now get back to your login screen and the problem is solved.