<Jordan_U> tom-macbook: sudo apt install grub-pc grub-efi-amd64-signed

<Jordan_U> tom-macbook: It looks like you currently have grub legacy installed. The command I gave will install packages for grub2 for both BIOS and UEFI. (Either of which will only result in a system that is bootable if you otherwise have the appropriate partitions like a BIOS Boot Parittion and an EFI System Partition mounted to /boot/efi/ (those are two separate partitions)).

<tom-macbook> Jordan_U, Is there any way to have both?

<Jordan_U> tom-macbook: Yes. You just need to have the things I mentioned setup.

<Jordan_U> tom-macbook: If you want to be able to move the drive from one computer to another you'll also need to run "sudo grub-install --removeable –target=x86_64-efi".

Hopefully this will suffice?
I have run "sudo apt install grub-pc"
then I ran "sudo apt install grub-efi-amd64-signed"

Now "sudo grub-install" returns with "No target device"