package usrmerge 24ubuntu3 failed to install/upgrade: installed usrmerge package post-installation script subprocess returned error exit status 1

[themusicgod1]

in #1924850
> Can each one of you please open a new bug reports, using `ubuntu-bug` tool with full apt output logs. -
Dimitri John Ledkov (xnox)

ubuntu 20.04 LTS to 21.04 upgrade

ProblemType: Package
DistroRelease: Ubuntu 21.04
Package: usrmerge 24ubuntu3
ProcVersionSignature: Ubuntu 5.4.0-88.99-generic 5.4.140
Uname: Linux 5.4.0-88-generic x86_64
ApportVersion: 2.20.11-0ubuntu65.3
Architecture: amd64
CasperMD5CheckResult: unknown
Date: Mon Oct 11 17:09:47 2021
ErrorMessage: installed usrmerge package post-installation script subprocess returned error exit status 1
PackageArchitecture: all
Python3Details: /usr/bin/python3.9, Python 3.9.5, python3-minimal, 3.9.4-1
PythonDetails: /usr/bin/python2.7, Python 2.7.18, python-is-python2, 2.7.18-9
RebootRequiredPkgs: Error: path contained symlinks.
RelatedPackageVersions:
 dpkg 1.20.9ubuntu1
 apt 2.2.4ubuntu0.1
SourcePackage: usrmerge
Title: package usrmerge 24ubuntu3 failed to install/upgrade: installed usrmerge package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to hirsute on 2021-10-11 (0 days ago)

[themusicgod1 (themusicgod1)]

FATAL ERROR:
Both /sbin/update-grub and /usr/sbin/update-grub exist.

[themusicgod1 (themusicgod1)]

and like
https://bugs.launchpad.net/ubuntu/+source/usrmerge/+bug/1924850/comments/13
moving update-grub and then grub-install from /sbin/ to /root
and then rerunning /usr/lib/usrmerge/convert-usrmerge resulted in

The system has been successfully converted.

[Launchpad Janitor (janitor)]

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