Comment 23 for bug 1894667

Please run "ls /sys/class/backlight/" to see what backlight interfaces are available.

You may also want to try the kernel parameter for backlight such as below

        acpi_backlight= [HW,ACPI]
                        { vendor | video | native | none }
                        If set to vendor, prefer vendor-specific driver
                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
                        of the ACPI video.ko driver.
                        If set to video, use the ACPI video.ko driver.
                        If set to native, use the device's native backlight mode.
                        If set to none, disable the ACPI backlight interface.