I'm late for this thread (https://forum.recalbox.com/topic/6517/4-1-unstable-need-testers-for-a-bluetooth-major-improvement/34), but bring a feedback.
I tested a 8bitdo SFC30 (Firmware version 4.0.) with Rpi 3 internal bluetooth and everything worked fine, except for one thing: the hotkey combination to save/load games doesn't works. I tried it using a wired Xbox One controller and i was able to save and load using the specifics hotkeys shortcuts.
What can be happening?