I'm on a fresh installation of Ubuntu and planning to install i3wm. Unfortunately, the brightness is completely stuck on the maximum, rendering it basically torture to use during the night. Neither the brightness keys on my keyboard nor the brightness slider on the top right dropdown do anything. The brightness keys do show that the brightness is decreasing on the slider but it doesn't actually change at all. Please help! I'm using a Lenovo Flex 5 14.
Edit: It's definitely not the laptop itself's problem because the brightness buttons worked when I was on Windows and when I shut down the computer, the space around the Shut Down prompt is darker.