Unable to change brightness of Thinkpad X1 Extreme 4K using function keys

Question

I disabled Secure Boot in BIOS and reinstalled Ubuntu 18.10. I followed the steps described in the following link to modify the grub. However, after executing sudo update-grub and rebooted the system, I still cannot change the brightness using the function keys.

Brightness key not working Ubuntu 16.04 LTS

Answer 1

Ok, I've figured it out for me, at least with ubuntu 18.04 as of 2/11/2019.

1. Install ubuntu nvidia drivers:

   # use auto-install (as mentioned by @Ibrahim)
   sudo ubuntu-drivers autoinstall
   

2. Edit the GRUB_CMDLINE_LINUX_DEFAULT entry in the /etc/default/grub to the following:

   GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nvidia.NVreg_EnableBacklightHandler=1"
   

3. Update grub configuration after edit and save:

   sudo update-grub
   

4. Reboot:

   sudo reboot