Public bug reported: I tried all the things here- https://askubuntu.com/questions/1238620/i-was-unable-to-update-to-ubuntu-20-from-ubuntu-18-04
But it still gives the same error - Could not calculate the upgrade 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'. I have also attached the 'main.log' file. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: ubuntu-release-upgrader-core 1:18.04.40 ProcVersionSignature: Ubuntu 4.15.0-123.126-generic 4.15.18 Uname: Linux 4.15.0-123-generic x86_64 ApportVersion: 2.20.9-0ubuntu7.19 Architecture: amd64 CrashDB: ubuntu CurrentDesktop: ubuntu:GNOME Date: Wed Nov 11 14:57:50 2020 InstallationDate: Installed on 2019-01-23 (657 days ago) InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725) PackageArchitecture: all SourcePackage: ubuntu-release-upgrader UpgradeStatus: Upgraded to bionic on 2020-11-11 (0 days ago) VarLogDistupgradeAptclonesystemstate.tar.gz: Error: command ['pkexec', 'cat', '/var/log/dist-upgrade/apt-clone_system_state.tar.gz'] failed with exit code 127: Error checking for authorization org.freedesktop.policykit.exec: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying VarLogDistupgradeTermlog: ** Affects: ubuntu-release-upgrader (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug bionic dist-upgrade third-party-packages ** Attachment added: "main.log" https://bugs.launchpad.net/bugs/1903870/+attachment/5433444/+files/main.log -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1903870 Title: can not update to 20.04 LTS. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1903870/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs