I had 18.04 and upgraded to 20.04. At first dual boot. After installing, it showed a list of errors and never initiated the system. I went back to 18.04, everything was OK.
Installed again, but this time leaving only 20.04. The installation was good. I didn't have any errors by the end, but when it is supposed to initiate the system I get a black screen (with Ubuntu and the logo at the bottom).
I tried to disable UEFI in the BIOS (the other option is Auto for Legacy or UEFI), but instead of the dark screen with the logo, I get a totally black screen turning on and off repeatedly.
Notebook Samsung 700z Intel Core i5