I am a convinced Linux user. Currently my home PC runs Ubuntu 18.04 with HPLIP 3.18.5, from the official Ubuntu repository.
Having to purchase a new All-in-One printer, I chose to go with HP because, to my knowledge, they have the best Linux support, through the HPLIP tool.
My new HP Envy Photo 7830 is a great device, looking and feeling strong and professional. However, to be fully happy with it, I have to get rid of a couple annoyances:
- I can't get the Automated Document Feeder to work: when I put a sheet into it, it does feel it, sounding a beep. And yet, when I push the SCAN button in the Simple Scan app, the ADF doesn't get the sheet and what I get is a white (empty) page.
- The paper tray extension is properly ejected every time a sheet is about to go out the printer. However, it then gets stuck in that position, even when I switch the printer off: the only way to get it back inside the tray is pushing it by hand, with the risk to break the internal gears.
What I would like instead is (I assume this is the normal behavior when using Windows):
- when any sheet(s) are inside the ADF, they get priority over manually fed sheets and they are therefore automatically fed into the scanning surface and scanned;
- when the printer is switched off, the tray extension is automatically withdrawn into place, preserving it from accidental breakage.
I know that it is possible to configure printer-specific settings from the printer driver's GUI, accessible both from HPLIP and from Ubuntu's Settings/Printers . I would not be surprised if the above issues could be easily fixed simply by entering the right control words in the right spots. But, unfortunately, here stops my knowledge 
Please, please, does anyone out there know what control command could do the magic for me, assuming that I'm guessing right? And, if I am wrong, is there another way to succeed?
Thank you all for any suggestion to make me completely happy, at least with my new printer?
Cheers!
Michele