@substring, Believe me i really understand your point !
I din't knew that is only beta works when i bought the RPI3B+ this morning.
Dear @substring ,
thank you for your help, i will check this topic.
For your knowledge, I try to find an answere since sevral hour and everytime someone ask, all answere are: "please "find by yourself dumb".
also, i had recalbox on rpi2, works without any additional things to do. i was thinking, it was the same on rpi3B+
Last thing, i am not complain, just asking