For all those who want to use Recalbox with the GameHat, here is how to do it:
recalbox-user-config.txt file in the root of the card:hdmi_force_hotplug=1
avoid_warnings=1
max_usb_current=1
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 640 480 60 6 0 0 0
hdmi_drive=2
display_rotate=0
recalbox.conf file like this:
controllers.gpio.enabled=0 to controllers.gpio.enabled=1.controllers.gpio.args=map=1,2 to controllers.gpio.args=map=5 gpio=5,6,13,19,21,4,26,12,23,20,16,18,-1