I have tried installing ubuntu with efi and also with it disabled. The live disk opens with a black screen giving options. (this screen is supposed to indicate EFI boot) when you choose install ubuntu or try ubuntu, the disk spins and the screen just turns black. I have read around on this site and all suggestions seem to revolve around ubuntu actually installing. I have searched this under "could not open efi\boot\efi fallback.efi14 error variable root isn't set" answers to this were unhelpful since the suggestions all seemed to assume that ubuntu was installing. Since it isn't installing I cannot use the terminal.
After wasting loads more time including setting the computer back to default I attempted another install from the disk. Still ended up with a black screen.
I tried pressing buttons starting with the F buttons. It turned out that the display just needed the brightness button increasing. By default the HP had gone to a low brightness setting when I was installing Ubuntu. Once I saw purple I knew I had won. I have been using Ubuntu for years with no problems. I test drove Ubuntu on the disk then went for a full install.