The slider on top right for brightness does not work but volume and microphone sliders do work. As a temporary workaround, xrandr can set brightness and a shell script is about as convenient as using the slider. The script is below and should be used as ./brightness.sh 0.5 where 0.5 is the brightness you want to set it to. 1 is maximum and 0 is minimum.
#!/bin/bash
Sets brightness on scale of 0 to 1
xrandr --output DP-0 --brightness $1
Edit: DP-0 is the screen, it is usually the default but not always. If this script does not work for you, check your screen id.
