Once GRUB is open, press the “e” key to edit the first highlighted entry “Ubuntu”.If your computer uses EFI or UEFI, continuously tap the “ESC” (escape) key after turning on your PC. After turning on your PC, hold the right SHIFT key to get to the GRUB bootloader if your computer uses a BIOS.It’s much like the issue I described here on a Fedora Linux system. This is due to a video mode issue that causes the system to halt or freeze.
This event can also occur on a fresh installation or when updates are installed. After upgrading a computer from Ubuntu 16.04 LTS to Ubuntu 18.04 LTS or Ubuntu 18.04 LTS to Ubuntu 20.04 LTS, during boot the screen goes blank (turns black), all HD disk activity halts, and the system becomes frozen.
