@hunterln only God knows.
Recalbox is an entirely volunteer job, so a beta will be release when developers bring it to a state stable enough for general use. Before that it doesn't make any sense, because users would be complaining about stuff not working as expected. It is that simple.
I just got a raspberry pi3, installed recalbox 4.0 on it and tried to set up my gamepads.
No trouble with 8bitDo NES pro, nor with an USB generic gamepad.
I tried to set up my Mad Catz C.T.R.L.R with this topic's solution.
Adding a line in the joystick rule file didn't work at first because of device name.
Indeed, the sdptool command on the MAC address told me the device's name is not "Mad Catz C.T.R.L.R", but "HID Gamepad".
The CTRLR switch is set on the gamepad.
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