The bug described in
QTBUG-8115 is still not solved.
I installed a printer (named pur) on my Linux server in cups. My Linux Clients need to use this remote printer. The Client use this address in his printers.conf:
With qt-based programs like Okular (21.12.2) the printing dialoge does not show any settings of the remote printer (like double sided, etc.).
I compared is to non qt-based programs like Evince (40.4) which download the ppd for the remote printer correctly. On the server I get in the /var/log/cups/error_log:
D [09/Feb/2022:15:27:09 +0100] [Client 285] GET /printers/pur.ppd HTTP/1.1
Download of the ppd file is iniciated correctly by Evince. Evince then shows all availaby printer-specific settings of the remote printer correctly.
But qt-based Okular does not ask for the necessary ppd-file. As a result, Okular does not show the printer-specific settings of the remote printer. Even worse is the fact that it modifies the standard settings: If the remote printer is double-sided, Okular resets it to single-sided.
The Screenshot shows Okular on the lift side and Evince on the right side. Left Okular does not show any settings, right Evince shows the settings correctly.