package shim-signed 1.50+15.4-0ubuntu7 failed to install/upgrade: installed shim-signed package post-installation script subprocess returned error exit status 1

[Ilya]

idk dude it just popped up at the end of ubuntu's installation

ProblemType: Package
DistroRelease: Ubuntu 21.04
Package: shim-signed 1.50+15.4-0ubuntu7
ProcVersionSignature: Ubuntu 5.11.0-25.27-generic 5.11.22
Uname: Linux 5.11.0-25-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
.proc.sys.kernel.moksbstate_disabled: Error: [Errno 2] Нет такого файла или каталога: '/proc/sys/kernel/moksbstate_disabled'
ApportVersion: 2.20.11-0ubuntu65.1
Architecture: amd64
BootEFIContents:
 BOOTX64.CSV
 grub.cfg
 grubx64.efi
 mmx64.efi
 shimx64.efi
CasperMD5CheckResult: pass
Date: Tue Jul 27 13:11:57 2021
EFITables:
 июл 27 15:59:33 ilya-Q2542N kernel: efi: EFI v2.31 by American Megatrends
 июл 27 15:59:33 ilya-Q2542N kernel: efi: ACPI 2.0=0xc98a5000 ACPI=0xc98a5000 SMBIOS=0xca867418 MOKvar=0xc8107000
 июл 27 15:59:33 ilya-Q2542N kernel: secureboot: Secure boot disabled
 июл 27 15:59:33 ilya-Q2542N kernel: secureboot: Secure boot disabled
ErrorMessage: installed shim-signed package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2021-07-27 (0 days ago)
InstallationMedia: Ubuntu 21.04 "Hirsute Hippo" - Release amd64 (20210420)
Python3Details: /usr/bin/python3.9, Python 3.9.5, python3-minimal, 3.9.4-1
PythonDetails: N/A
RelatedPackageVersions:
 dpkg 1.20.9ubuntu1
 apt 2.2.4ubuntu0.1
SecureBoot: 22 0 0 0 0
SourcePackage: shim-signed
Title: package shim-signed 1.50+15.4-0ubuntu7 failed to install/upgrade: installed shim-signed package post-installation script subprocess returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[death (sniper-xxx123)]

Please fix this. We cannot install Ubuntu 21.04 clean.
It's impossible for regular user.

[Julian Andres Klode (juliank)]

There are three possible causes

- firmware bug
- kernel bug
- user error (read-only variables), though why does that give I/O rather than ENOSPACE

I'm going to reassign this one to linux for a check on the kernel side, but I suspect it's a firmware issue.