Normally you should be able to adjust screen brightness by simply left clicking on your battery icon assuming it’s in your bottom right screen icon tray. That then produces a brightness slider. But when I left click on the icon I get nothing of the sort. How do I add this/ get it back to how it was?
One request. It seems that you are using the zen kernel. Will it be possible for you to please shift, on a temporary basis, to the normal mainline Linux kernel or LTS Linux kernel and see if you still face the issue?
Not permanently, just for one small session to check. You can continue to use the zen kernel post this check.