@Cheib : Great success:
I used the dtbo from an old rpi firmware (firmware-1.20181112.zip) with this md5sum:
9621a8827d53ea92e8d16e5795dd2f9a
moved the entry in /boot/config.txt (dtoverlay) before the include recalbox-config.txt and the gpu_mem entries
now I can see the hifiberry card in sound settings. 
