thank you for your quick response!
i guess if i ever happen to have a spare wii u pro controller or can get one for cheap, i'll send it your way :).
in the meantime can someone recommend a bluetooth dongle that works with the wii u pro controller? maybe some of you have a working setup.
the recalbox wiki lists so many bluetooth dongles that it is hard for me to decide. so if someone has had good experiences with one particular dongle, let me know.
cheers tim
ps.: just another idea: couldn't you just implement retropie's solution and implement it in recalbox (sorry if that is a totally noobish idea, i got no clue of such things)