Comment 87 for bug 736743

OK so I actually found out how to do the above thing.

So apply the provided patch for /etc/grub.d/00_header.
Original used for patching is from Ubuntu 17.10 (GRUB 2.02~beta3-4ubuntu7.3).
Move or create your grub env block file to efi partition:
ubuntu original location: /boot/grub/grubenv
patch location: /boot/efi/EFI/ubuntu/grubenv
Run update-grub2 to create the new grub config.

I do not know what EFI specs or something like that
says abount using EFI partition for the GRUB env block,
but it DOES work for me.