Cannot turn off keyboard backlight permanently

Hi,

I have a Chuwi GemiBook laptop (with Intel Celeron J4115 CPU) and i'd like to turn off its keyboard backlight permanently.
It can be turned off with one of the Fn keys, but the turned off state is not persisted through reboots.
EDIT: I'm running Debian stable with i3wm.

Found the following ArchWiki article:
https://wiki.archlinux.org/index.php/keyboard_backlight
But i don't seem to have any keyboard related devices under /sys/class/leds.

Code:$ brightnessctl --list
Available devices:
Device 'intel_backlight' of class 'backlight':
Current brightness: 3200 (33%)
Max brightness: 9600

Device 'phy0-led' of class 'leds':
Current brightness: 1 (100%)
Max brightness: 1

Device 'mmc2::' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 255

Device 'input0::scrolllock' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 1

Device 'input0::capslock' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 1

Device 'mmc1::' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 255

Device 'input0::numlock' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 1

Device 'mmc0::' of class 'leds':
Current brightness: 0 (0%)
Max brightness: 255intel_backlight is the display brightness and setting phy0-led to 0 does not seem to have any effect.

Checked the BIOS as well, didn't find any settings related to the keyboard backlight.

I'd really appreciate any advice.
Thanks in advance!