Upgrade from ubuntu 18.04 to ubuntu 20.04 error

[Paul]

I ran the terminal cmd sudo do-release-upgrade -d and errored out
An unresolvable problem occurred while calculating the upgrade.

This was caused by:
* Upgrading to a pre-release version of Ubuntu
This is most likely a transient problem,
please try again later.
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'.

from logs /var/log/dist-upgrade/main.log

2020-09-25 17:14:27,701 DEBUG updateSourcesList()
2020-09-25 17:14:27,710 DEBUG rewriteSourcesList() with mirror_check
2020-09-25 17:14:27,711 DEBUG ['ubuntu-minimal', 'ubuntu-standard']
2020-09-25 17:14:27,711 DEBUG Checking pkg: ubuntu-minimal
2020-09-25 17:14:27,712 DEBUG BaseMetaPkg 'ubuntu-minimal' has no candidate.origins
2020-09-25 17:14:27,843 ERROR NoDistroTemplateException raised: Error: could not find a distribution template for Ubuntu/bionic
Traceback (most recent call last):
  File "/tmp/ubuntu-release-upgrader-l840cs21/DistUpgrade/DistUpgradeController.py", line 538, in rewriteSourcesList
    distro.get_sources(self.sources)
  File "/tmp/ubuntu-release-upgrader-l840cs21/DistUpgrade/distro.py", line 93, in get_sources
    (self.id, self.codename))
DistUpgrade.distro.NoDistroTemplateException: Error: could not find a distribution template for Ubuntu/bionic
2020-09-25 17:14:27,844 DEBUG get_distro().enable_component("main") failed, overwriting sources.list instead as last resort
2020-09-25 17:14:27,845 DEBUG examining: 'deb http://archive.canonical.com/ubuntu bionic partner'
2020-09-25 17:14:27,845 DEBUG verifySourcesListEntry: deb http://archive.canonical.com/ubuntu focal partner
2020-09-25 17:14:27,846 DEBUG url_downloadable: http://archive.canonical.com/ubuntu/dists/focal/Release
2020-09-25 17:14:27,846 DEBUG s='http' n='archive.canonical.com' p='/ubuntu/dists/focal/Release' q='' f=''
2020-09-25 17:14:27,924 DEBUG entry 'deb http://archive.canonical.com/ubuntu focal partner' updated to new dist
2020-09-25 17:14:27,924 DEBUG examining: 'deb http://archive.ubuntu.com/ubuntu focal main restricted # auto generated by ubuntu-release-upgrader'
2020-09-25 17:14:27,924 DEBUG entry 'deb http://archive.ubuntu.com/ubuntu focal main restricted # auto generated by ubuntu-release-upgrader' is already set to new dist
2020-09-25 17:14:27,925 DEBUG examining: 'deb http://archive.ubuntu.com/ubuntu focal-updates main restricted # auto generated by ubuntu-release-upgrader'
2020-09-25 17:14:27,925 DEBUG entry 'deb http://archive.ubuntu.com/ubuntu focal-updates main restricted # auto generated by ubuntu-release-upgrader' is already set to new dist
2020-09-25 17:14:27,925 DEBUG examining: 'deb http://security.ubuntu.com/ubuntu focal-security main restricted # auto generated by ubuntu-release-upgrader'
2020-09-25 17:14:27,925 DEBUG entry 'deb http://security.ubuntu.com/ubuntu focal-security main restricted # auto generated by ubuntu-release-upgrader' is already set to new dist
2020-09-25 17:14:27,927 DEBUG running doUpdate() (showErrors=True)
2020-09-25 17:14:33,447 DEBUG openCache()
2020-09-25 17:14:33,780 DEBUG Comparing 5.3.0-40 with
2020-09-25 17:14:33,781 DEBUG Comparing 5.4.0-42 with 5.3.0-40
2020-09-25 17:14:33,782 DEBUG Comparing 5.4.0-47 with 5.4.0-42
2020-09-25 17:14:33,782 DEBUG Comparing 5.4.0-48 with 5.4.0-47
2020-09-25 17:14:33,830 DEBUG /openCache(), new cache size 10189
2020-09-25 17:14:33,830 DEBUG need_server_mode(): run in 'desktop' mode, (because of pkg 'ubuntu-desktop')
2020-09-25 17:14:33,831 DEBUG quirks: running PreDistUpgradeCache
2020-09-25 17:14:33,831 DEBUG running Quirks.PreDistUpgradeCache
2020-09-25 17:14:33,831 INFO installing python-is-python2 because python-minimal was installed
2020-09-25 17:14:33,831 DEBUG Installing 'python-is-python2' (python-minimal was installed on the system)
2020-09-25 17:14:33,831 INFO removing python-minimal because python-is-python2 is being installed
2020-09-25 17:14:33,831 DEBUG Removing 'python-minimal' (python-is-python2 is being installed on the system)
2020-09-25 17:14:34,524 ERROR Dist-upgrade failed: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'
2020-09-25 17:14:34,528 DEBUG abort called
2020-09-25 17:14:34,529 DEBUG openCache()
2020-09-25 17:14:34,730 DEBUG Comparing 5.3.0-40 with
2020-09-25 17:14:34,731 DEBUG Comparing 5.4.0-42 with 5.3.0-40
2020-09-25 17:14:34,731 DEBUG Comparing 5.4.0-47 with 5.4.0-42
2020-09-25 17:14:34,731 DEBUG Comparing 5.4.0-48 with 5.4.0-47
2020-09-25 17:14:34,747 DEBUG /openCache(), new cache size 2695

I ran all updates and upgrades to ubuntu 18.04

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38 [origin: unknown]
ProcVersionSignature: Ubuntu 5.4.0-42.46~18.04.1-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.17
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity:Unity7:ubuntu
Date: Fri Sep 25 17:23:36 2020
InstallationDate: Installed on 2019-08-06 (416 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-09-25 (0 days ago)

[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.