There is a third (next to this one and this one), quite pretty fuckup with HP printer's settings. Even though they have full hardware support for duplex printing, this feature (as good as many others -- like manual page feeding) comes disabled.
There are actually two huge fuckups here:
- Printer ships to you with one of the most important (at least to eco-fucks) feature disabled and you have to go to it's web configuration (because -- like in this case -- most configurations settings are not available via touchscreen). You need to access Paper Configuration to be precise and change duplex (manual paper feed and other useful features) from disabled to enabled state.
Even bigger fuckup is that if you install a driver for this printer before changing above, it will install itself with duplex printing disabled completely. And you won't be able to duplex-print anything on duplex-enabled printer! You will be forced to uninstall entire printer driver and reinstall new one again, after applying above changes.