I tested patching out the likmailtransport-data <Breaks> libkf5mailtransport-data relation in the Packages file from a clean minimal install of trixie + mbox-importer installed, and it makes the full-upgrade pass without removing mbox-importer.
We need to keep the likmailtransport-data <Replaces> libkf5mailtransport-data relation since both packages ship the /usr/share/config.kcfg/mailtransport.kcfg file. I’d question the seriousness of this issue since using mbox-importer only really makes sense when pulled by kmail, and when kmail is installed apt is smart enough to not remove it during full-upgrade. -- Aurélien
