SUMMARY *** NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols. See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports *** STEPS TO REPRODUCE 1. Open Discover 2. Click Settings 3. Click Software Sources OBSERVED RESULT "Software Sources" requires a password, but does not accept the system password. EXPECTED RESULT Expected the system password to be accepted, as it is the only password entered since installation. SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
"Software Sources" is separate app provided by the Ubuntu folks; you would need to report this bug to them at https://bugs.launchpad.net/. I think the product name is "software-properties"
Looks like it is a KDE problem after all, just not a problem in Discover. *** This bug has been marked as a duplicate of bug 452532 ***