SUMMARY
I have a network printer that `lpinfo -v` can discover as an lpd printer. When I try to add that printer through system settings -> add printer, it does show up as a discovered network printer, but when I then click on that printer both the address and queue input fields are empty. I would have expected those to be filled in with the details from the discovery.

STEPS TO REPRODUCE
1. Open System Settings
2. Go to Hardware -> Printers
3. Click on Add Printer
4. Click on the printer under "Discovered Network Printers", make sure this is a lpd printer

OBSERVED RESULT
The right side of the "Add Printer" dialog shows empty input boxes for both "Address" and "Queue".

EXPECTED RESULT
The "Address" and "Queue" input boxes to contain the values that have been discovered.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 5.24.0 (but also existed on earlier versions)
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
After I manually set the address in the input box, the "Next" button was still disabled, however if you click on any other item on the list and then going back to the network printer the "Next" button becomes enabled.
Also, it seems that the queue field isn't being used. I had to enter the address as 'printer/queue' and left the queue empty for the url to be correct. When I entered the printer name in address, and the queue name in queue the printer that was added did not have the queue in it's connection.
When you prepend the address with `lpd://` it shows as if all is well but after you click "Finish" no printer was added and no error was shown.