I have success after wandering in the weeds for a while.
I was distracted by the New Printer dialog that showed this:
    HP Officejet Pro K550 (joy, 169.254.74.169)

Well “joy” is the name of our Airport Express device, which is what the printer is plugged into. So that must be it, right? All my attempts to use it failed.

My research ran into something called hp-setup, and something else called hp-doctor, and the latter did some software updates for me, but kept reporting that there was nothing found on the network.

Then I realized that the “HP Officejet Pro” line had me fooled: the Airport Express “joy” was at 192.168.1.191.

So I used “Find Network Printer” for host “joy” and it added a line, “JetDirect(joy)” as it had before. And that was it. The lack of description for the printer, and the distracting descriptive line that was incorrect, are what fooled me.

Thanks for your help and patience. :) 
________________

On Feb 20, 2016, at 12:53:03, Victor Odhner <vodhner@cox.net> wrote:

I found HPLIP was already installed. I added HPIJS for good measure.
I was able to select a driver "HP Officejet Pro K550 hpijs, 3.15.2”.

The printer is still “not responding.”

I didn’t see HPLIP mentioned anywhere in the driver choices.
_________

Details follow. 

Selected the driver and asked for a test page:

  Description: HP Officejet Pro K550
  Make and Model: HP Officejet Pro K550 hpijs, 3.15.2
  Result: Processing - The printer is not responding.

Printer’s light is green, and it’s working from the Macbook.
I notice that the printer icon doesn’t show in the taskbar.

Tried printer-make “Generic (recommended)”:
   There are ESC/P, GDI, IBM-Compatible, OAKT,
   PCL*, PDF, PostScript*, Raw Queue, text-only and ZjStream.
   I chose PCL 3 (recommended).
   Two drivers are offered: Foomatic and K550 hpijs, 3.15.2 [en].
   I chose the hpijs.

Print Test Page —> Connecting to Printer —> not responding.
Same as before.
__________________

On Feb 20, 2016, at 10:59:13, Brian Cluff <brian@snaptek.com> wrote:

Do you have hplip installed?  That printer is reported to "Work Perfectly" on the list of supported printers.

http://www.openprinting.org/printer/HP/HP-OfficeJet_Pro_K550

It says:
"For basic printing functionality use the HPIJS driver . For advanced functionality such as printer status, maintenance features, scanning and photo card unload use the HPLIP driver (which includes HPIJS)."

Brian Cluff

On 02/20/2016 10:44 AM, Victor Odhner wrote:
Keith wrote: "/HP is very good about providing drivers for their
printers/.” Not necessarily so, after they weary of supporting it.

We have an HP OfficeJet K550, a nice printer that’s working well but
maybe as much as 10 years old. My recently installed Mint system doesn’t
show the K550; it comes up with a different printer’s name, labeled as
“recommended,” and that driver doesn’t work: it finds the printer but
when I try to print it declares that it is not connected.

My Macbook has no problem finding it and printing. My son’s Win10 uses
the PCL3 Class Driver and works OK for plain text, but Win10 can’t find
a K550 driver. He says that HP has removed drivers and other support for
this printer, which is at “end of support”.

I did find this:
http://hplipopensource.com/hplip-web/models/officejet/officejet_pro_k550.html
… which claims to have have a K550 driver.

I haven’t tried to figure out how hplip works, since I can move
documents to my DropBox and print from the Macbook.
___________

On Feb 20, 2016, at 09:12:48, Brian Cluff <brian@snaptek.com
<mailto:brian@snaptek.com>> wrote:

On 02/20/2016 06:49 AM, Keith Smith wrote:
I have not researched how to configure the print to fax and how to scan
using Linux... not sure it will work in these capacities with Linux.

In my experience it is very likely that you WOULD be able to scan with
an HP all-in-one.  HP is very good about providing drivers for their
printers.

Brian Cluff

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