Comment 0 for bug 1915082

Backlight controls do not have any effect on a Macbook7,1 running Ubuntu 18.04.
Ubuntu is installed in Legacy BIOS mode and uses the proprietary Nvidia drivers.
The apple_backlight directory appears in /sys/class/backlight and while different brightness values can be set, they have no effect on the backlight's emitted brightness.
The backlight remains at full brightness.

I have tested the following kernel parameters but they have no effect.

acpi_backlight=vendor
video.use_bios_initial_backlight=0
acpi_osi=
video.use_native_backlight=1