I tried to upgrade from ubuntu 18.04 tp 20.04 using the below command sudo update-manager -d I am getting the below error
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'.