I've now tested one only non-postscript printer, an Epson WF-7520, that won't be a widely used item. I configured the printer via web interface, following the procedure at http://wiki.ipfire.org/en/addons/cups/start
. There being no PPD file for this printer in IPFire, I selected one from a working installation in Leap 42 and got the printer configured
It worked, from Windows 8.1-64, via IPFire CUPS, with either the ethernet and USB interfaces connected to the IPFire host.
Could not get it to work from openSUSE Leap 42. Some of the prerequisites are present in Core 110:
/lib/cups/filters/epson-escpr & /lib/cups/filters/epson-escpr-wrapper. CUPS log in IPFire showed no errors & web interface reports all jobs completed - but no printout - indeed no activity at all at printer end.
Unable to test my other non-postscript printer, a Brother MFC-J6910DW, from either Windows or Linux. Brother have filters that are more specific to each model and none are present in IPFire's /lib/cups/filters.