Keyboard stopped working on application launcher/dashboard/menu and on "alt+space" launcher. The text field is focused, but no key events seems to be handled by the control. All the other apps, Dolphin and Konsole for example seems to work in this regard. Not sure what I did before I started to experience this. Any help on this, thanks? I'm running 5.8.5 Plasma on 4.9.1 Kernel (Ubuntu 16.04).

I came to the forums for this same problem. It is incredibly frustrating. I am glad someone else has this problem, but I hoped somebody already had the answer...

The worst part is that authentication dialogues (say, kdesudo, or wallet) don't get any text, so the only way to input a password is to type it inside konsole, select it, and paste it with the middle mouse button. In the process, your password is visible on the screen, and gets copied to the clipboard. Ouch.

Some more info about my configuration: the problem appeared yesterday, after having upgraded from Plasma 5.6 to Plasma 5.8 via Kubuntu official backports. Using 16.04.