SUMMARY
When using Settings->Configure Software Sources the popup can't authenticate for root permissions.

STEPS TO REPRODUCE
1. Have your useraccount be able to use sudo using its own password.
2. Have root account with different password enabled.
3. Select "Settings->Configure Software Sources".
4. The popup that comes is titled "Run as root -- KDE su" and displays as command "/usr/bin/software-properties-kde --attach ######## --dont-update"

OBSERVED RESULT
5. No matter which password you type (own or root's), it is NOT accepted.


EXPECTED RESULT
5. You should be allowed to use either your own password or that of root's.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 19.04
KDE Plasma Version: 5.15.4
KDE Frameworks Version: 5.56.0
Qt Version: 5.12.2

ADDITIONAL INFORMATION
I don't actually use this feature because i configure my sources via command-line in /etc/apt/{sources.list,sources.list.d/*}