Oh boy... this bug report is open since Jan 2023 now (the bug is much older) and nothing happens from #Qt side.
It's a small thing: The printing settings don't show the field for entering a custom PIN or other text required to do e.g. password protected printing. It works in CUPS, it works with LibreOffice's weird printer dialogue...
But since Qt's QPrinterDialog doesn't work, it won't work in KDE... -.-
Just wanted to check if I could contribute anything... well... need a Qt Account, need a Gerrit account... where's the repo anyway? Ah, in the Qt Developer Portal... oh, need a Qt Account for that... sorry, that's way too much red tape.