Well the most well known one is Geos for the C64
https://youtu.be/_4nthOx8sA4?si=AiK9bRxRQwV3MB0f
There's also this Atari homebrew
https://youtu.be/T14dL9MeMHE?si=cGtsZGWILYi4jcql
And yes the IIGS had one
https://youtu.be/_4nthOx8sA4?si=AiK9bRxRQwV3MB0f
There's also this Atari homebrew
https://youtu.be/T14dL9MeMHE?si=cGtsZGWILYi4jcql
And yes the IIGS had one