grub-efi crashes on upgrade; install script did not offer correct choice of GRUB partitions or option to override auto-detected (package grub-efi-amd64-signed 1.187.3~20.04.1+2.06-2ubuntu14.1 post-installation script subprocess returned error exit status 12)

[Brent Spillner]

I have GRUB booting from a UEFI binary on /dev/sda1, which is my only UEFI partition. However, the post-install script offered only a choice to install to /dev/sda5, with no option for manual override. Attempting to install to /dev/sda5 returned the (expected) error messages

NTFS signature is missing.
Failed to mount '/dev/sda5': Invalid argument
The device '/dev/sda5' doesn't seem to have a valid NTFS.

and caused the apt upgrade for the grub-efi-amd64 package to fail.

I think there are likely two problems here: (1) an issue with UEFI partition detection, and (2) failure to provide any obvious manual override mechanism for this vital part of system configuration, which would be absolutely necessary for use cases like multiple drives with UEFI partitions, or unusual boot sequences.

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: grub-efi-amd64-signed 1.187.3~20.04.1+2.06-2ubuntu14.1
ProcVersionSignature: Ubuntu 5.13.0-52.59~20.04.1-generic 5.13.19
Uname: Linux 5.13.0-52-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.26
Architecture: amd64
CasperMD5CheckResult: skip
Date: Mon Apr 24 21:21:45 2023
ErrorMessage: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 12
InstallationDate: Installed on 2022-01-31 (448 days ago)
InstallationMedia: Ubuntu 20.04.3 LTS "Focal Fossa" - Release amd64 (20210819)
Python3Details: /usr/bin/python3.8, Python 3.8.10, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: N/A
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3.2
 apt 2.0.9
SourcePackage: grub2-signed
Title: package grub-efi-amd64-signed 1.187.3~20.04.1+2.06-2ubuntu14.1 failed to install/upgrade: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 12
UpgradeStatus: No upgrade log present (probably fresh install)