Cannot change brightness or connect to external monitor

It doesn’t detect external monitor, the hotkeys don’t work to change brightness, and the slider to change it doesn’t even show up in Power Settings!

I also cannot make Desktop Cube Animation work when switching desktops, but I don’t know how related that would be

Start by telling us

  1. Laptop make and model

  2. Graphics hardware details as reported by the following

/usr/sbin/hwinfo --gfxcard
  1. Current boot parameters
cat /proc/cmdline

You’re using Plasma, I assume?

If you wouldn’t mind filing a bug report, it’d help yourself and the community. The KDE team is responsive and can help you sort through things, but we also need every bug report we can get right now in order to iron out Plasma 5.11.95 issues before the Leap 15 release in a few months. Provided that Tumbleweed is updated and running 5.11.95.

Also, is the brightness slider faded out or just not displayed at all? Because you have to click the box next to it to be able to adjust the slider.