I just successfully printed to my Z3100 from my 2013 MacBook Pro running Mojave. I first had to uninstall the printer and all HP software, then download the latest driver from HP (raster driver version 52.0). All works as expected, except that I find that I have to launch the printer utility separately - I no longer see it in System Preferences/Printers & Scanners/Options & Supplies, nor in the Print dialog within PS.
I too am looking at new hardware, but I'm worried because I see HP has Catalina drivers for the Z3200, but not the Z3100. We'll see how that goes.
Regarding the problem of printing the last inch, I solved that on El Capitan by running older drivers (version 26.0). I could not get these drivers to install on Mojave though, so I expect I will have the problem when I print on sheet media.
