Failed to adjust display brightness

I’ve just run into problems with the Display and Monitor setting in the KDE Plasma environment which says “the module display and monitor is not a valid configuration module” and it further says the diagnosis is “the desktop file settings-hardware-display.desktop does not specify a library”, any suggestion?

I’m running 4.16.9-1-ARCH.

Hmm this forum might not be the best place to ask for support on this issue. Did you install Plasma in ArchLabs?

Yes.

Where should I find the support on this issue?