just for curiosity, I tried running this extension on Windows, Inkscape 1.1-dev (ed187d8, 2019-12-24). I got the error message below. I would suggest contacting the original developer, which is: Copyright (C) 2013 Sebastian Wüst, sebi@timewaster.de
hth, Alvin
.................................................. Traceback (most recent call last): File "plotter.py", line 22, in <module> from inkex.ports import Serial File "C:\APP\Temp\inkscape_devel\share\inkscape\extensions\inkex\ports.py", line 25, in <module> import pty File "C:\APP\Temp\inkscape_devel\lib\python3.8\pty.py", line 11, in <module> import tty File "C:\APP\Temp\inkscape_devel\lib\python3.8\tty.py", line 5, in <module> from termios import * ModuleNotFoundError: No module named 'termios'