Hi, I have the same probem that @Valippo.
I have a SFC30 8bitdo gamepad that works fine on the previous 8.x.x version of recalbox (raspberry 4 or 3)
I have updated the SFC30 firmware to 4.20.
I start the pad with START + R.
The SFC30 is well paired and recognized by the recalbox but impossible to configure it.
At the configuration step, when the recalbox interface ask me to press a button, nothing happen, I have tried all button sbut the recalbox seems to not detects inputs on the SFC30.
Here is my configuration :
Raspberry 4 2GB
NEPSI 4 Case
SFC30 8 bitdo gamepad
Thank you for your feedback.