Following this suggestion I have disabled Google Keyboard application. My entire system has crashed and upon restart, I can't see that application in application list, so I could reenable it.
How to restore Google Keyboard, so it would start appear again in Settings > Apps > All?
All disabled apps are listed on Settings > Apps > Disabled, where you can re-enable any of it.
If for some reasons or in certain situations, Disabled tab does not appear (like in my case) and restarting device does not help, then you can open menu in Apps (three dots in right top corner) and select Reset app preferences.
After confirming all your disabled apps become enabled again.
I found it. Go to Apps and tap the three dots in the upper right corner and select "Show system". There's the Gboard now.
