Unable to upgrade ubuntu 18.04 to 20.04

[Thameem Ansar]

This was likely caused by:
 * Unofficial software packages not provided by Ubuntu
Please use the tool 'ppa-purge' from the ppa-purge
package to remove software from a Launchpad PPA and
try the upgrade again.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.41
ProcVersionSignature: Ubuntu 5.4.0-56.62~18.04.1-generic 5.4.73
Uname: Linux 5.4.0-56-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.20
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Mon Dec 7 11:44:52 2020
InstallationDate: Installed on 2019-12-17 (355 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-12-07 (0 days ago)
VarLogDistupgradeTermlog: