So I just found a more elegant way to upgrade an installed openSUSE Leap from 15.2 to 15.3…
well, turns out that cyrus imap was dropped from 15.3 because the package seemed to have been abandoned. That means with “zypper dup” it would have been uninstalled.
I’m just glad I noticed before actually running the upgrade, unlike the poor guy who initially filed the bugreport…