sudo is not configured here. Surely it should work with pkexec in Buster.
This message saying not to run it with sudo was posted at https://unix.stackexchange.com/questions/463352/how-to-run-kde-partition-manager-with-no-root-password-set but no suggested correct usage was forthcoming: "Don't run partitionmanager like this. Things might break if you use sudo (note, I am the maintainer of KDE Partition Manager). – Andrius Štikonas <https://unix.stackexchange.com/users/169537/andrius-%c5%a0tikonas> Aug 27 '18 at 11:47 <https://unix.stackexchange.com/questions/463352/how-to-run-kde-partition-manager-with-no-root-password-set#comment846654_463354>"
Andrius Štikonas <https://unix.stackexchange.com/users/169537/andrius-%c5%a0tikonas> is the maintainer at https://github.com/KDE/partitionmanager
