Hi,
so I am now trying 4.25 and whenever I drag Sky Atmosphere actor in the scene, the area below horizon remains pitch black. Few pages back, @SebHillaire mentioned there will be an added option to define atmospheric scattering inside the planet volume or something, but it appears it’s still not present. 
To me, the new atmosphere is still not usable due to this.
And one more question. How do I actually get physically accurate ratio of sun light to sky light? If I enable directional light to be sky atmosphere sun, the intensity value still has an effect, so the proportion of the sun light strength to the sky light intensity seems pretty much random. All the other physically based sky models I know have this taken care of.