Can't print - 'Backend' failed
I figured out a workaround.  (Of course after struggling with this for weeks, I figure it out just after posting the question.)
When adding the printer, the dialog asks for &quot;Name&quot;, &quot;Location&quot; and &quot;Use&quot;.  &quot;Use&quot; defaults to &quot;Secure AirPrint&quot;, but changing this to &quot;AirPrint&quot; fixes the problem.  It's a Xerox printer, FWIW.