The error is: Calling 'apt-install grub-efi-amd64-signed' failed
https://askubuntu.com/questions/789998/16-04-new-installation-gives-grub-efi-amd64-signed-failed-installation-target
The error is: Calling 'apt-install grub-efi- amd64-signed' failed
https:/ /askubuntu. com/questions/ 789998/ 16-04-new- installation- gives-grub- efi-amd64- signed- failed- installation- target