grub-install simply copies the binaries from /usr/lib/grub to /boot/efi, and configures the EFI system variables to point there. Just mount the ESP in /boot/efi and run grub-install. It still requires a device argument for backward compatibility, but it is ignored so you can specify anything you want. The Ubuntu installer just runs grub-install dummy.
↧
Answer by psusi for How to create efi partition and install GRUB bootloader manually
↧