Upgrade aborted with an error, coud not calculate upgrade, unresolvable problem occured while calculating the upgrade

[Lokesh]

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

 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.

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'.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.40
ProcVersionSignature: Ubuntu 5.4.0-144.161-generic 5.4.229
Uname: Linux 5.4.0-144-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.25
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Thu Mar 9 15:20:39 2023
InstallationDate: Installed on 2023-03-08 (0 days ago)
InstallationMedia: Ubuntu 18.04.6 LTS "Bionic Beaver" - Release amd64 (20210915)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to focal on 2023-03-09 (0 days ago)
VarLogDistupgradeTermlog: