per code in ubiquity:/usr/share/grub-installer/grub-installer
it install grub-efi-amd64-signed first, and then install shim-signed.
(grub_package=grub-efi-amd64-signed as the code run to here.)
===
apt-install $grub_package || exit_code=$?
case $grub_package in *-signed) apt-install shim-signed || true apt-install grub-pc || true
;;
esac
===
per code in ubiquity: /usr/share/ grub-installer/ grub-installer amd64-signed first, and then install shim-signed. grub-efi- amd64-signed as the code run to here.)
*- signed)
apt-install shim-signed || true
apt-install grub-pc || true
it install grub-efi-
(grub_package=
===
apt-install $grub_package || exit_code=$?
case $grub_package in
;;
esac
===