1) install the nvidiabl module from https://github.com/guillaumezin/nvidiabl (Downloads > nvidiabl-dkms_0.69_all.deb);
2) add a line with 'nvidiabl' in /etc/modules;
3) add 'acpi_backlight=vendor' to the GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub;
4) run update-grub.
Workaround from https:/ /bugs.launchpad .net/ubuntu/ +source/ linux/+ bug/803051 (tested on LG R590-5700 only):
1) install the nvidiabl module from https:/ /github. com/guillaumezi n/nvidiabl (Downloads > nvidiabl- dkms_0. 69_all. deb); =vendor' to the GRUB_CMDLINE_ LINUX_DEFAULT in /etc/default/grub;
2) add a line with 'nvidiabl' in /etc/modules;
3) add 'acpi_backlight
4) run update-grub.
Read this issue if you have problems after reboot: https:/ /github. com/guillaumezi n/nvidiabl/ issues/ 14