I found that in KDE System Settings/Energy saving I actually can control brightness by moving sliders and clicking Apply or OK. The system just does not react on Fn+F5/F6. So probably the problem is easier than it seemed initially.
I found that in KDE System Settings/Energy saving I actually can control brightness by moving sliders and clicking Apply or OK. The system just does not react on Fn+F5/F6. So probably the problem is easier than it seemed initially.