Ubuntu OS upgrade unsuccessful due to unofficial packages

[Sagar Das]

Log message after the reading the system state information:

1. Calculating the changes
2. Could not calculate the upgrade
3. An unresolvable problem occured while calculating the upgrade.
4. This was likely caused by: * Unofficial software packages not provided by Ubuntu. Please use tool 'ppa-purge' from the ppa-purge package to remove a launchpad PPA.

Tried to ppa-purge but issue still persists.
Had ROS installed. So uninstalled it-
>> sudo apt-get purge ROS-*

Also removed all the unrequired packages-
>> sudo apt-get autoremove

Problem still persists.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 5.4.0-48.52~18.04.1-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.17
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Fri Oct 2 16:39:21 2020
InstallationDate: Installed on 2019-10-03 (365 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-10-02 (0 days ago)

[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!