Further communication with the bug reporter on IRC indicates that the release upgrade 20.04 LTS -> 22.04 LTS succeeded, just unbound failed to start on 22.04 with the configuration file which worked on 20.04. So this is is NOT an issue with the release-upgrader.
Further communication with the bug reporter on IRC indicates that the release upgrade 20.04 LTS -> 22.04 LTS succeeded, just unbound failed to start on 22.04 with the configuration file which worked on 20.04. So this is is NOT an issue with the release-upgrader.