There are 3 repositories under pen-plotters topic.
lineboi3000 is a way cool graphical interface for drawing, painting, adding EFX, and then sending your designs to a pen plotter or creating animations
Vector graphics software to generate HPGL output to drive a plotter
A browser-based tool to render single-line fonts and export text as SVG files to be used with CNC machines like pen plotters.
Misc. plotter utilities
Pen Plotter Webserver for RPI0