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

[Chris Guiver]

The Lubuntu 18.04 to Lubuntu 20.04 upgrade path is not supported by the
Lubuntu team because of the switch of desktop. If you refer to the
release notes of any release starting with 18.10 you'll note

"Note, due to the extensive changes required for the shift in desktop
environments, the Lubuntu team does not support upgrading from 18.04 or
below to any greater release. Doing so will result in a broken system.
If you are on 18.04 or below and would like to upgrade, please do a
fresh install."

https://lubuntu.me/focal-1-released/

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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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