Error when trying to switch to Ubuntu 20.04 LTS

[Julien]

I am using Ubuntu 18.04 LTS on an Odroid N2, during my umpteenth attempt to upgrade to the current LTS version; that I try by a terminal or with the utility of update; I always end up getting an error message regarding PPAs.
However, I unchecked all the sources, but impossible to understand where it could come from, I did the following command:
"sudo apt-get update -y && sudo apt-get upgrade -y && sudo apt-get dist-upgrade -y" before attempting to upgrade the OS, but I still get the same result.

I would really like to avoid going over to doing a full reinstallation, which would mean reinstalling my various programs and scripts; being a small home production server.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 2:18.04.38 [origin: unknown]
Uname: Linux 4.9.241-77 aarch64
ApportVersion: 2.20.9-0ubuntu7.24
Architecture: arm64
CrashDB: ubuntu
CurrentDesktop: MATE
Date: Wed Jul 7 19:34:54 2021
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2021-07-07 (0 days ago)
VarLogDistupgradeLspcitxt:

VarLogDistupgradeTermlog: