Adding CesiumSunSky turns scene white

Is there some configuration required when adding CesiumSunSky to a map? I ask since the view is just white.

Notice that I also use UltraDynamicSky - and removing it yields same result. The idea is to disable UDS and enable CesiumSunSky during flying.

Yes, you need to enable “Extend default luminance range”. The Quick Start guide walks through it: