Is it BIOS (in which case you have grub-pc
installed) or (U)EFI (in which case you have grub-efi-ia32 or
grub-efi-amd64 installed)?
I have UEFI (which I just learned), but grub-pc is installed. I assume that's because the UEFI has legacy mode turned on.
Can I move from grub-pc to grub-efi-amd64? There are a few random webpages that suggest it's difficult; I haven't found an authoritative source that says how to do it.
I didn't notice anything in the
gnu.org help-grub archive that seemed relevant, but I may have missed something.