Cannot upgrade Ubuntu mate 18.04 to 20.04

[Toto]

This is a similar bug as Bug #1887544 which I have been following for 6 month but is now closed.
"upgrade from 18.04 to 20.04 fails to calculate if python-dbg is installed".

@Brian Murray (brian-murray) suggested :
"Could you please open a new bug report using "ubuntu-bug ubuntu-release-upgrader"? Once you've done that let me know and I'll have a look at the logs."

I could do this update on two other Unbuntu mate 18.04 machines (that I use less. ie fewer softwares).

You should have the logs attached. Let me know if you need me to do extra actions.
I have tried 10 times to upgrade the past motnhes.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.44
ProcVersionSignature: Ubuntu 5.4.0-78.87~18.04.1-generic 5.4.124
Uname: Linux 5.4.0-78-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.24
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: MATE
Date: Wed Jun 30 07:28:49 2021
InstallationDate: Installed on 2019-05-11 (780 days ago)
InstallationMedia: Ubuntu-MATE 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2021-06-30 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update-manager.release-upgrades: 2021-05-05T18:06:10.677012

[Toto (chomisyann)]

Images Update process failing

[Toto (chomisyann)]

Selected repos

[Brian Murray (brian-murray)]

Reviewing the files from your upgrade attempt you have installed nodejs from a location other than the offical Ubuntu archive. This version of nodejs is greater than the one in the official archive and is keeping some python packages installed which then prevents the upgrade from being calculated. Please remove nodejs along with any other packages from that archive and disable the archive. After that you can try upgrading again and if it still fails open a new bug report. Thanks and good luck!

[Toto (chomisyann)]

This issue is closed.
Thanks for your Help Brian; you saved my day !
I managed to upgrade to 20.04 today.
After removing all the node package I could find in Synaptic package manager.

As an improvement, it could be nice to clarify the end user explanation for the failure to upgrade.
If I had basically your previous recommandation in-app this would have helped.
Instead I have been facing a generic error message :
https://launchpadlibrarian.net/524231674/upgrade20-putython-fails.jpg
A lot of developper in node need the latest version of node , as it is evolving so fast .

Anyhow thanks a lot for your support