Hello Tom or Jasem
I have stellarmate on a RPi4.
I have Arduino connected to RPi4
I run KStars/Ekos on my Mac.
I am also testing this on a bench.
I may be trying things without going through the right sequence of events to get it to work.
I have attached a zip file of what Tom has on the GIT page.
Could you perhaps please give me the steps I should follow to get the Mac side of things set up. 
Then which of the Arduino Sketches I should use for it to be compatible with the Mac side set up.