after insert & remove the SD an unknown number of times, i think i broken the sd connector 
i flashed an 8gb emmc i have with RC4 but i only get a BLACK screen
i think the emmc is not supported, but, is there any way to use the emmc please?
Did you switch the position of the little white switch In the Back of the xu4? It’s the thing responsible to boot from either eMMC or microSD.
yes ofcourse, it’s the first thing i did 
I think the libreelec version does support eMMC booting for the xu4 though. But if I’m not mistaken, and I’ve got 3 of the darn things, doesn’t the syslinux have to be altered before you try booting it from the emmc? Check the github for more info on the xu4 boot emmc subject. I’m pretty sure something from the initialization has to be changed for the lakka build because I know it worked perfectly from the micro sd.
Speak of the devil.
Openelec works out of the box without any settings modification Libreelec did not even shw the lakka logo
EDIT: i read the post unfortunately i can’t boot ubuntu from sdcard (to flash lakka image on emmc) because i have somehow damaged sdcard connector