I have a xeon 2670 v3 and a rx580 8gb, both are updated. I couldn’t lower brightness even using brightness controller and xbacklight command
You may need to add one of the available kernel command-line options.
Please copy and paste terminal output using preformatted text instead of posting screenshots of text. Please edit your post accordingly.
acpi_backlight=none
acpi_backlight=video
acpi_backlight=vendor
It didn’t worked
You tried each one? Did you check the log each time and compare to a log without?
Please see [HowTo] Find error logs
You forgot something…