Turn off keyboard backlight when shutting down Linux

In my Kubuntu the right place is /sys/class/leds/.

# ls /sys/class/leds/
dell::kbd_backlight  input4::capslock  input4::numlock  input4::scrolllock  phy0-led  xpad0

Most certainly, if your Metoo Zero backlight is there, it will be something other than dell::kbd_backlight, so the below commands are just examples.

# ls "/sys/class/leds/dell::kbd_backlight"
brightness  device  max_brightness  power  start_triggers  stop_timeout  subsystem  trigger  uevent
# cat "/sys/class/leds/dell::kbd_backlight/max_brightness"
2

This number suggests my backlight has three states. I can run (as root):

# echo 0 > "/sys/class/leds/dell::kbd_backlight/brightness"
# echo 1 > "/sys/class/leds/dell::kbd_backlight/brightness"
# echo 2 > "/sys/class/leds/dell::kbd_backlight/brightness"

It turned out the states are: 0=off, 1=dimmed, 2=bright.

If it works for you, make your Linux execute the appropriate command before it shuts down (I believe the way to do it is distribution-dependent).