I just tried to set the CUPS Printer Default Options to "Long Edge" (my idea was to 'force' even gnome/non-KDE apps to use duplex), and got this "fun" result (see attached screenshot):
--- snip ---
Error: The following options are conflicting:
Double-Sided Printing: Long Edge (Standard)
Duplexer Installed: Installed
Please change one or more of the options to resolve the conflicts.
--- snap ---
Aha, so if I have a duplexer I cannot print duplex. Great. Of course changing the "Duplexer Installed:" to "Not Installed" does not allow me to set the "Double-Sided Printing:" option to "Long Edge (Standard)" either.
I forgot to say I have an OfficeJet Pro 8500A.
I just tried to set the CUPS Printer Default Options to "Long Edge" (my idea was to 'force' even gnome/non-KDE apps to use duplex), and got this "fun" result (see attached screenshot):
--- snip ---
Error: The following options are conflicting:
Double-Sided Printing: Long Edge (Standard)
Duplexer Installed: Installed
Please change one or more of the options to resolve the conflicts.
--- snap ---
Aha, so if I have a duplexer I cannot print duplex. Great. Of course changing the "Duplexer Installed:" to "Not Installed" does not allow me to set the "Double-Sided Printing:" option to "Long Edge (Standard)" either.