This is probably not the right place to report it, but the version of KPM in discover is 1.2.1 even though 2.x seems to be stable. Reproducible: Always
Yeah, unfortunately noone packages it for Kubuntu :(. Even older version is in Debian. 1.2.1 for Kubuntu was packaged by Jonathan Riddell but he now works on Neon (which by the way has much newer version of KDE Partition Manager). Try to report this bug to Kubuntu developers (probably on Launchpad)...
Do you perhaps know where exactly I could report this? KDE is really not the most transparent and well-documented community for a noob like me.
Maybe try here: https://launchpad.net/ubuntu/+source/partitionmanager