installed shim-signed package post-installation script subprocess returned error exit status 1

[Sai Vinoba]

Release: Kubuntu 21.04
SW, version: ubiquity, 21.04.19

How to reproduce:
1) Try installing Kubuntu (I tried from live-session, not tried direct install)

Expected:
Installation completes normally.

Actual:
Installer crashes with error message `installed shim-signed package post-installation script subprocess returned error exit status 1`.

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: ubiquity 21.04.19
ProcVersionSignature: Ubuntu 5.11.0-16.17-generic 5.11.12
Uname: Linux 5.11.0-16-generic x86_64
ApportVersion: 2.20.11-0ubuntu65
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.461
CurrentDesktop: KDE
Date: Fri May 28 20:01:57 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/kubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Kubuntu 21.04 "Hirsute Hippo" - Release amd64 (20210420)
RebootRequiredPkgs:
 linux-image-5.11.0-16-generic
 linux-image-5.11.0-17-generic
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Sai Vinoba (saivinob)]

This also affects UM 21.04. Possibly others.

Also, this happens with both Secure Boot on as well off. I read bugs #1928434 and #1925010 but they were upgrades and fresh installation worked. In my case installation itself is failing.

On UM though, even after installed showed failed message, I went ahead and choose the new entry from Grub menu (of another install) but the screen stays on UM logo. Using text mode shows some sort of kernel panic or unable to mount message which I could not capture.

[Launchpad Janitor (janitor)]

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

[Boulesteix (photonoxx)]

Try to install both Kubuntu & Ubuntu 21.04 and get the same error and impossible to complete the installation.