Found the solution to turn on-off the display! 
That is too stupid to be real…but… something is different in 8.9, in order to turn on/off the display, the path is different
from
/sys/class/backlight/rpi_backlight/bl_power
to
/sys/class/backlight/backlight/bl_power
I spent days to try to load different driver from vc4-kms-dpi, the old vc4-fkms-dpi etc… but all that was needed was just to change the path 