Brightness control not working in GNOME - Ubuntu 18.04

[sonof]

Brightness control is not working in GNOME, under any login manager (GDM, Lightdm, SDDM) and under kernel boot up.

Under GNOME there is not any UI control to control brightness (or they are not showing to me), and keyboard buttons also does not work. The only way to set brightness in GNOME is by using xbacklight, which by default requires elevated rights (sudo or as root).

I have installed MATE and KDE desktop environments, and although brightness does not work in Linux kernel tty, in MATE and KDE brightness buttons work out of the box as expected. Also brightness settings persists within each DE on its own, unlike GNOME's case (which brightness has to be set manually with xbacklight).

Even though brightness under booting process does not work, that is not a big issue since it works under Xorg (at least) once DE is loaded (MATE and KDE handle it properly), screen dim is set to user configuration value. But GNOME is not working as it should work for a default and flagship DE. Of course, would be great if session manager and kernel could set and save brightness level too.

I have installed Ubuntu 18.04 and also installed the subsequent updates, so my system is up to date.

My computer is a laptop HP Omen 15-ce0xx:
* CPU: Intel® Core™ i7-7700HQ CPU @ 2.80GHz × 8
* GPU: Nvidia GeForce GTX 1060 with Max-Q Design
* Storage: SSD NVME Samsung
           HDD SATA
* Chipset Intel

System is Ubuntu 18.04 64 bits
Kernel version 4.15.0-20-generic
Using NVIDIA proprietary drivers.

Please tell me if you need more information.

[EDITED 2018-05-18: cleanup and update]

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[sonof (son-of666)]

I've made a workaround. Since hardware buttons doesn't work, GNOME didn't ship UI controls to set an essential feature that is screen brightness, and brightness can be manually set by using xbacklight:

1. I created a PolKit policy allowing non-admin groups to use xbacklight tool.
2. I created two custom keybindings in GNOME settings to set brightness level with a key combination. In my case:

* Shift+F1 runs "xbacklight -dec 10" which decreases brightness each time is pressed by 10 (hardware button is Fn+F1);
* Shift+F2 runs "xbacklight -inc 10" which increases brightness each time is pressed by 10 (hardware button is Fn+F2).

[sonof (son-of666)]

Somehow it was resolved after some update.