[Bug 1900365] [NEW] Upgrade from Lubuntu 18.04 to 20.04 not possible

[Isving Wolfsdottir]

Public bug reported:

Ubuntu-Release:
Description:	Ubuntu 18.04.5 LTS
Release:	18.04

Upgrade to 20.04 doesn't work


"do-release-upgrade" crashes already with:
---------------- 
It could not be determined which system updates are available 

An unsolvable problem occurred during the calculation of System Update
to.

This was caused by: 
* System update to a pre-release version of Ubuntu 
This is most likely a temporary problem, please try again later. 
If none of these apply, please report the error using the 
Command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. 
If you want to investigate this yourself, you will find a description in the 
log files under "/var/log/dist-upgrade" Details on 
System update. Look especially at "main.log" and 
"apt.log" on. 
---------------

I've already tried without success to remove 3rd party package sources
like Steam and WireGuard and removed the installed programs.

Unfortunately I haven't also additional information what happened.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.40
ProcVersionSignature: Ubuntu 4.15.0-121.123-generic 4.15.18
Uname: Linux 4.15.0-121-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
Date: Mon Oct 19 01:04:02 2020
InstallationDate: Installed on 2019-01-01 (656 days ago)
InstallationMedia: Lubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=de_DE
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-10-18 (0 days ago)
VarLogDistupgradeTermlog:

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug bionic dist-upgrade

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https://bugs.launchpad.net/bugs/1900365

Title:
  Upgrade from Lubuntu 18.04 to 20.04 not possible

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  Ubuntu-Release:
  Description:	Ubuntu 18.04.5 LTS
  Release:	18.04

  Upgrade to 20.04 doesn't work

  
  "do-release-upgrade" crashes already with:
  ---------------- 
  It could not be determined which system updates are available 

  An unsolvable problem occurred during the calculation of System Update
  to.

  This was caused by: 
  * System update to a pre-release version of Ubuntu 
  This is most likely a temporary problem, please try again later. 
  If none of these apply, please report the error using the 
  Command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. 
  If you want to investigate this yourself, you will find a description in the 
  log files under "/var/log/dist-upgrade" Details on 
  System update. Look especially at "main.log" and 
  "apt.log" on. 
  ---------------

  I've already tried without success to remove 3rd party package sources
  like Steam and WireGuard and removed the installed programs.

  Unfortunately I haven't also additional information what happened.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.40
  ProcVersionSignature: Ubuntu 4.15.0-121.123-generic 4.15.18
  Uname: Linux 4.15.0-121-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.18
  Architecture: amd64
  CrashDB: ubuntu
  Date: Mon Oct 19 01:04:02 2020
  InstallationDate: Installed on 2019-01-01 (656 days ago)
  InstallationMedia: Lubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  PackageArchitecture: all
  ProcEnviron:
   LANGUAGE=de_DE
   TERM=xterm-256color
   PATH=(custom, no user)
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2020-10-18 (0 days ago)
  VarLogDistupgradeTermlog:

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