Hello, recently got my boards and went to install Retrogame and found an easier option to install using:
sudo bash retrogame.sh
Then chose any option on installer and modified: /boot/retrogame.cfg for the button mapping.
Had a chance to test it out last night, got all the buttons working on right side. (I think I missed something on left side as it wasn't working.) Probably missed a ground wire or something.
Anyhow figured I'd mention this install script since it was surprisingly easy to use.