edubuntu fails to fully install and messes with any other installation

[Abdul-Razak Sawal Alhassan]

Setting up edubuntu-artwork (15.12.1) ...
/var/lib/dpkg/info/edubuntu-artwork.postinst: 18: update-gconf-defaults: not found
dpkg: error processing package edubuntu-artwork (--configure):
 installed edubuntu-artwork package post-installation script subprocess returned error exit status 127
Errors were encountered while processing:
 edubuntu-artwork
E: Sub-process /usr/bin/dpkg returned an error code (1)

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 5.8.0-38.43~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-38-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.14
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: GNOME
Date: Mon Jan 18 17:23:43 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
InstallationDate: Installed on 2021-01-09 (9 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
Symptom: installation
UpgradeStatus: No upgrade log present (probably fresh install)

[Chris Guiver (guiverc)]

I don't see how this relates to the installer (ubiquity), which also appears to have been run many days ago ("Installed on 2021-01-09 (9 days ago)") so package changed

[Chris Guiver (guiverc)]

Thank you for taking the time to report this bug and helping to make Ubuntu better.

To seek support, you can ask a question at https://answers.launchpad.net/ubuntu. You can also find help with your problem in the support forum of your local Ubuntu community http://loco.ubuntu.com/ or asking at https://askubuntu.com or https://ubuntuforums.org, or for more support options please look at https://discourse.ubuntu.com/t/community-support/709