Comment 7 for bug 1812863

Verification-done on cosmic with grub2 / grub2-signed:

ubuntu@ubuntu:~$ dpkg -l grub-efi\* | grep ii | awk '{ print $2" "$3 }'
grub-efi-amd64 2.02+dfsg1-5ubuntu8.1
grub-efi-amd64-bin 2.02+dfsg1-5ubuntu8.1
grub-efi-amd64-signed 1.110.1+2.02+dfsg1-5ubuntu8.1

ubuntu@ubuntu:~$ sudo update-grub
Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.18.0-14-generic
Found initrd image: /boot/initrd.img-4.18.0-14-generic
Found linux image: /boot/vmlinuz-4.18.0-10-generic
Found initrd image: /boot/initrd.img-4.18.0-10-generic
Found Windows Boot Manager on /dev/sda1@/EFI/Microsoft/Boot/bootmgfw.efi
Adding boot menu entry for EFI firmware configuration
done

update-grub now correctly shows sourced files, as expected.