Unable to upgrade from 18.04 to 20.04

[Ian Kenworthy]

Could not determine 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'.

I have removed all ppa: - no difference

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.40
ProcVersionSignature: Ubuntu 4.15.0-122.124-generic 4.15.18
Uname: Linux 4.15.0-122-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Sat Oct 31 23:09:04 2020
InstallationDate: Installed on 2017-01-22 (1378 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-10-31 (0 days ago)
VarLogDistupgradeTermlog:

[Brian Murray (brian-murray)]

Reviewing the files from your upgrade attempt you seem to have enabled a PPA that provides Xorg packages. This will prevent the upgrade as that PPA contains package version numbers greater than the release to which you are upgrading. You can revert the PPA by installing the ppa-purge package from the official Ubuntu archive and then running 'sudo ppa-purge ppa:oibaf/graphics-drivers'. After that you can try upgrading again and if it still fails open a new bug report. Thanks and good luck!

[Ian Kenworthy (iankenworthy2001)]

It looks different.

When I run sudo ppa-purge ppa:oibaf/graphics-drivers this is what I get

ik@Desktop:~$ sudo ppa-purge ppa:oibaf/graphics-drivers
[sudo] password for ik:
Updating packages lists
W: Skipping acquire of configured file 'restricted/binary-amd64/Packages' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'restricted/binary-i386/Packages' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'restricted/i18n/Translation-en_GB' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'restricted/i18n/Translation-en' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'restricted/dep11/Components-amd64.yml' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'restricted/dep11/icons-48x48.tar' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'restricted/dep11/icons-64x64.tar' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
W: Skipping acquire of configured file 'restricted/cnf/Commands-amd64' as repository 'http://archive.ubuntu.com/ubuntu bionic InRelease' doesn't have the component 'restricted' (component misspelt in sources.list?)
PPA to be removed: oibaf graphics-drivers
Warning: Could not find package list for PPA: oibaf graphics-drivers

and these files exist in /etc/apt/sources.list.d
/etc/apt/sources.list.d/oibaf-ubuntu-graphics-drivers-bionic.list
/etc/apt/sources.list.d/oibaf-ubuntu-graphics-drivers-bionic.list.distUpgrade
the contents of both are just 2 commented lines

and no items in sources.list ot sources.list.distUpgrade referring to xorg-oibaf

Any guidance would be appreciated
Thanks