I bought an Armatron "robot arm" but I haven't been able to find a guide to computer-controlling it - any tips are welcome !
You basically have to ignore the internals and mount motors to the outside. Still, it's doable, as these instructions from 1984 demonstrate. Probably can make something far better today.
https://archive.org/details/color-computer-magazine-1984-04
The internals however are quite fascinating on their own and an amazing accomplishment of mechanical engineering for a toy.
Hint: Nobody knows clankers better than clankers. Ask one!
Looks like it is completely electromechanical and not IC driven.
https://www.starborneworks.com/?p=22