Installing 20.04 is a nightmare! Please assist?

If the nomodeset option works, you can make it permanent by sudo vi /etc/default/grub or some other editor you know, find quiet splash, add nomodeset, save, exit, then sudo update-grub

it would look like GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"

I cannot explain why install worked the first time but any subsequent install fails with black screen.