@jostein_olsen managed to get plt.show() working in his set-up, but had to change something to do so. We’ve had a cursory look and were unable to figure out what was going wrong without a deeper dive 
If anyone else in this thread knows, then please do sing out! Otherwise, there is a workaround right now to use the Bitmap library, as follows by @c.poupin Python 3 Skelitonization - plt.show() not work - #7 by c.poupin