The above command shows what I just did no more than half an hour ago when I mounted then cloned the install I was running from external SSD to test the new install of Kubuntu 24.04 I have been running for days to my internal nvme drive. To boot from there as I now am. The files needing to be edited if wrong are the /tmp/efi/EFI/ubuntu/grub.cfg and /tmp/root/boot/grub/grub.cfg with possibly the /tmp/root/etc/fstab to check the partitions have been put into it correctly.