FWIW I've written an HPGL plotter emulator for Linux. Once the plot is sent from the instrument, it can be printed or saved in several file formats.
I've tested it on an HP8595E spectrum analyzer and HP8753C network analyzer.
The GPIB adapter (on the computer) must be capable of acting as a listener / talker. (Some devices will only act as a system controller.)
Available for download from
https://github.com/VK2BEA/HPGL-Plotter