Had issue of booting to grub command line Stuck at GRUB command line so ran suggestion of sudo update-grub
and then did a reboot.
Now computer fan come on but absolute no signal. No bios, grub or ubuntu signal. Am plugged into HDMI of external graphic card, ubuntu 20.04 and windows 10 dual boot.
Before sudo update-grub
had asrock bios appeared, then grub command line.
Very much https://xkcd.com/349/ moment.