Upgrade from 18.04.5LTS to 20.04LTS fails from terminal and upgrade tool with error "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." No package to be removed is mentioned

[Ian]

W: Skipping acquire of configured file 'contrib/binary-amd64/Packages' as repository 'http://ftp.iinet.net.au/pub/ubuntu bionic InRelease' doesn't have the component 'contrib' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'contrib/binary-i386/Packages' as repository 'http://ftp.iinet.net.au/pub/ubuntu bionic InRelease' doesn't have the component 'contrib' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'contrib/i18n/Translation-en' as repository 'http://ftp.iinet.net.au/pub/ubuntu bionic InRelease' doesn't have the component 'contrib' (component misspelt in sources.list?)

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 4.15.0-118.119-generic 4.15.18
Uname: Linux 4.15.0-118-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.9-0ubuntu7.17
Architecture: amd64
CrashDB: ubuntu
Date: Wed Oct 14 10:14:36 2020
InstallationDate: Installed on 2017-02-02 (1349 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_AU:en
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-10-13 (0 days ago)
VarLogDistupgradeTermlog:

[Ian (iwoolf)]

Calculating the changes

Could not calculate the upgrade

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'.

[Brian Murray (brian-murray)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1898152, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.