Hey @Scott_T , another solution, arguably simpler, is to add a default .efi to the VM. This can be done to the original VM before migrating or to the new VM after migrating. In the latter case, we assume you can access the new VM’s root.img using whatever mechanism you use to run the original VM - looks like you’re using Virtual Box; I’m using qemu.
Anyway, log into the VM and, as root, mkdir /boot/efi/EFI/BOOT alongside existing /boot/efi/EFI/ubuntu. Now copy contents of /boot/efi/EFI/ubuntu into /boot/efi/EFI/BOOT. Now cd to /boot/efi/EFI/BOOT and rename or copy grubx64.efi to bootx64.efi
If you made this mod to the new VM, shut it down and then run it with incus start NAME and it should now just work. If you made the mod to the original VM, I assume incus-migrate should leave those changes alone so you can run the newly migrated VM immediately.