I posted this in a similar thread. This workaround works flawlessly for me and doesn’t require any editing in Retropie:
Go to the 8bitdo official website, download and install the 8bitdo ultimate software on your PC or Mac, if not already done. Plug the 8Bitdo Arcade Stick to your PC or Mac with a USB cable and make sure your selector knob is in “X” mode (top left of the 8bitdo Arcade Stick) Start the 8bitdo Ultimate software On the right, in the button mapping panel, beside RT, associate RS instead. Do the same for LT except choose LS. Don’t forget to synchronize the controller (icon at the top) before disconnecting the USB cable. Connect your 8bitdo Arcade stick to the Retropie either via a USB cable, the 2. To 4G stick or Bluetooth. Push the start button to get to the main menu (you might need another controller or keyboard to make the selections initially). Select “configure input”. At first, make sure your selector knob is selected to DP (middle selection) to associate D-pad up, down, left, right. This time the RT and RS buttons will work flawlessly.Contributions to the project are always appreciated, so if you would like to support us with a donation you can do so here.
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