I have an unofficial Wiimote and it works fine with Recalbox 18.07.13 on my Rpi 3b+. Sometimes it indicates player number #1, but LEDs almost always blink. Another problems not detected =)
Also, I just bought the NES mini controller, connected it to Wiimote and tried it with Recalbox. And it works fine too! I guess, it's just a Wii classic controller with reduced number of buttons. The protocol is the same. Thus, I assume that the SNES classic gamepad will work fine too.
I guess it will be useful for someone, so I think that would be great to update the wiki article https://github.com/recalbox/recalbox-os/wiki/Compatibility-(EN)
P.S. BTW sorry for my bad English =D