Choosing any of the initial sound setups in YaST (Quick, Normal or Advanced)
and also selecting on "reset all" option disables sound card.

As a result I get no sound and the built-in sound device is missing from Plasma
5 configuration, instead, it shows a "dummy device".

Rebooting gets the sound working again.

I'm running a Dell E6440 laptop with Intel graphics and the following audio
devices:
8 Series/C220 Series Chipset High Definition Audio Controller
Xeon E3-1200 v3/4th Gen Core Processor HD Audio Controller