Your files from
https://github.com/PKHG/guidelab_paint work OK here in Linux (kubuntu 18.040 and Gimp 2.10.12
Attachment:
lab.jpg [ 146.68 KiB | Viewed 3034 times ]
What does not work in guidelab_paint is
Simple path shapes.py version 1.1 (size 114,638 B) although it works on its own.
That weird malformed circle? There is a post about it somewhere, a Gimp 2.10 bug, but I can not find it
Just for information arakne-shape-path-8 has a fixed for Gimp 2.10 version see:
viewtopic.php?f=9&t=17044&start=20#p238555Does shape-path-8 work with OSX ? I do not know.