Hi !
The GPIO implemntation is done with an joystick driver. Is there a possibility to have also Keybindings mapped via GPIO (eg. ESC, F1 …)
The GPIO driver is https://github.com/digitalLumberjack/mk_arcade_joystick_rpi is create joystick special files detected as simple joysticks by SDL. You can't bind the gpio events mapped to keyboard. But recalboxOS doesn't need any keyboard to work.
If not is it possible to implement adafruit retrogame gpio input?
No because it would be useless as recalbox works well with joysticks.
Is it possible to bind the joystick driver to use other GPIO pins?
Yes if you recompile the driver changing the button mapping. It will never be an option in recalbox as i want the system to stay user friendly (and noob friendly)