No brightness control 18.04 LTS: /sys/class/backlight is empty

I know this issue had been addressed in the past (like this, this, this, this, this, this and more), but none were actually given a definite answer.

To begin, I'm using a NVDIA GTX1080 Max-Q graphic card. Installed driver 390 (Can't seems to switch to 396, it automatically rolled back to 390 when I select in 'Additional Drivers'). And the folder /sys/class/backlight is empty, as mentioned.

Next, I try to disable Wayland in /etc/gdm3/custom.conf and that resulted with me greeted by black screen after login. Can't seems to enter grub mode by pressing Alt+Ctrl+F1. Referred answer here. Reinstalled Ubuntu many times just to be sure about this.

Then, tried the method as suggested here and here. Still didn't fix it.

Temporarily I'm using the bash script to adjust the brightness, but it would jump to maximum again if a prompt pop up, like Authentication or copying files.

Any actual way to fix this once and for all?

Solution 1:

xbacklight does not work for you, right?

In my case a workaround is use the line

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nvidia.NVreg_EnableBacklightHandler=1"

in the /etc/default/grub file.
The problem is explained here

Solution 2:

For me this worked on my old laptop with NVIDIA GeForce 410M graphics card, Intel Core i3.

I've tried all of those too and found this one working: you make a file into this folder /usr/share/X11/xorg.conf.d the file name should be this: cat 80-nvidia.conf

so this should be like : /usr/share/X11/xorg.conf.d$ cat 80-nvidia.conf

Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "NVS 3100M"
Option "RegistryDwords" "EnableBrightnessControl=1"
EndSection