With the latest updates from the Kubuntu backports PPA digikam can no longer be installed. According to aptitude this is due to: digikam : Depends: kipi-plugins (= 4:5.9.0-1ubuntu4) but 4:19.12.3-0ubuntu1~ubuntu19.10~ppa1 is to be installed. I see that digikam 6.4 that is in Focal is no longer dependant on kipi-plugins.