Comment 4 for bug 1975533

@Brian Murray, first, thank you so much for confirming the issue and creating this bug report.

Just to be clear, I finally was able to upgrade from groovy to impish by following the instructions in this post: https://blog.invid.eu/2022/02/24/upgrade-eol-ubuntu-server-from-20-10-to-21-10-an-upgrade-from-groovy-to-impish-is-not-supported-with-this-tool-ubuntu-ubuntugeek-ubuntu-linux-eol-upgrade/ ; see also the official documentation: https://help.ubuntu.com/community/EOLUpgrades

To the people new to this thread: see also my comment (https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1745754/comments/6) in the other bug report: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1745754 ; and my notes on the issue: https://gist.github.com/mikbuch/2c349e1281c69818b48893a460c5accb

@Brian Murray, your suggestion for the minimal fix is all OK, but I wonder if a more general mechanism could be implemented, to support upgrading from an EOL release X to a (EOL) release Y (as the `do-release-upgrade` already says/recognizes with which release there was a problem to which: "An upgrade from ‘groovy’ to ‘impish’ is not supported with this tool."). I don't fully grasp how the DistUpgrade.cfg work, maybe my issue is/was related only to groovy. Either way, if the current bug will be resolved, maybe it is also good idea to update the documentation on EOL upgrades, as well (https://help.ubuntu.com/community/EOLUpgrades).

I can help, and I will, as soon as I will get more familiar with the `do-release-upgrade` process.