In Reply to @mholt6 @mholt6 @MaartjeME The only other idea I can suggest is to live boot, chroot to that disk, mount-bind mtab and try to re-run update-grub
In Reply to @mholt6 @mholt6 @MaartjeME The only other idea I can suggest is to live boot, chroot to that disk, mount-bind mtab and try to re-run update-grub