System76 Boring Backlight, how to control it?

I ever dislike the keyboards with lights, today after firmware update on my NS5x_NS7xPU the keyboard..become "with backlight".
How to turn off?
I have tried this command as root

sh -c "echo 0 > /sys/class/leds/system76_acpi::kbd_backlight/max_brightness"
sh: line 1: /sys/class/leds/system76_acpi::kbd_backlight/max_brightness: Permission denied

When I press fn+f7 it appear a "monitor configuration" of Xfce4

When I run this command

echo 0 > /sys/class/leds/system76_acpi::kbd_backlight/brightness

the keyboard backlight is still on,