Cannot upgrade from 18.04 to 20.04

[kavish]

tried to updgrade from 18.04 to 20.04.
First try, got an error to purge ppa's which I did
Second try, got:

An unresolvable problem occurred while calculating the upgrade.

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.

Checked both log files without any clear indication of what is going wrong.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 5.4.0-42.46~18.04.1-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.15
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Mon Aug 3 16:33:57 2020
InstallationDate: Installed on 2020-04-23 (101 days ago)
InstallationMedia: Ubuntu 18.04.4 LTS "Bionic Beaver" - Release amd64 (20200203.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-08-03 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2020-08-02T14:48:55.126818

[Brian Murray (brian-murray)]

This is probably because you've installed gcc-10 packages from an archive other than the official Ubuntu one. From VarLogDistUpgradeAptclonesystemstate.tar.gz:

gcc-10-base 10-20200411-1 1

Removing that package and any other ones with the same version may allow you to complete the upgrade.

[Launchpad Janitor (janitor)]

[Expired for ubuntu-release-upgrader (Ubuntu) because there has been no activity for 60 days.]

[Yves BARBIN (barbin-yves)]

I already report about this bug
It was registered
I tried again today, expecting anything new, but I got nothing new

[Yves BARBIN (barbin-yves)]

in /var/log/main.log
I found what may be the key point, but I dont know what to do next:
ERROR Dist-upgrade failed: 'E:Erreur, pkgProblem::Resolve a généré des ruptures, ce qui a pu être causé par les paquets devant être gardés en l'état.'