Ok, so here is the UE4 Sphere Normal Map:
It acts this way:
In Material settings it looks weird:
3d object is just Box Brush:
"If its a sphere pointing outwards, the green channel should be bright on the bottom, not the top. if its looking correct in ue4, maybe you have Flip Green channel checked in the texture properties. So your 2nd attempt looks the most correct to me in terms of normal map orientation (ignoring the weird dark edge outline and facets).
Are you using UV channel0? tangent basis is only computed for UV0 so if you use anything else for normals it can give wrong results. Do you maybe have “tangent space normal = false” in your material?"
How do i flip channels in UE4 editor? And where is UV Channel0 and Tangent Space Normal settings?