This is a bit long but pretty straight forward:
I tried to install Ubuntu 18.04 from a USB key but instead of the grub menu I kept getting a burnt-out screen.
From this answer I understood that my NVIDIA graphic card is the problem, I'd edited the USB key grub menu and added the nomodeset flag. While this did work when I tried to access the installation I got the burnt-out screen again.
Long story short, I did the same (with nomodeset flag) with a 16.04 USB key and then upgraded to 18.04.
The problem now is that the resolution is stuck on very low and I cannot change it. I tried to remove the nomodeset flag from the grub but it isn't even there anymore.
I am guessing that it is still something to do with the NVIDIA drivers but it is way over my head and any help would be appreciated!