Instead of making a “smooth” cube in probuilder I did quickly one in Blender (to have exactly the same mesh on both Unity and Unreal side). Result:
The graphs are quite different tho. Shader Graph:
The one in ASE looks like that:
And in Unreal:
FYI, UE5 doesn’t like big displacement as those can cause shading issues. You have to extend bounds of your static meshes to have correct shading. (This isn’t an issue in UE4).