Same for me on Ubuntu 10.10 with a HP Color Laser CP4520 an HPLIP 3.10.2.
Under "Installable Options" I have a "Duplexer Installed" (On/Off - radio buttons) Option, but it's grayed out.
Under "Print Settings" I have an option "Double-Sided Printing" that I can set to "Long Edge (Standard)" - doesn't make it print double sided.
There is not "double-sided", "duplex", whatsoever option under "Miscellaneous"
Same for me on Ubuntu 10.10 with a HP Color Laser CP4520 an HPLIP 3.10.2.
Under "Installable Options" I have a "Duplexer Installed" (On/Off - radio buttons) Option,
but it's grayed out.
Under "Print Settings" I have an option "Double-Sided Printing" that I can
set to "Long Edge (Standard)" - doesn't make it print double sided.
There is not "double-sided", "duplex", whatsoever
option under "Miscellaneous"