I know this is old, and almost nobody do this BUT. Vray in 3ds max got me realistic lightning that is really difficult to achive on android, especially on android devices like PICO where you use hardware standalone on maximum. So I made raw diffuse and raw lightning textures in max-vray and made material in Unreal that looks great. But problem is when I turn off lights everything is black witch is logical 
When I put at emmisive in material editor in UE5 I just dont get good result. So is there any option to make something like global light of everything? How to solve this blackness? Also I have poor GPU hardware so its more easy for me to render on vray CPU 
if you don’t require specularity or any lighting you could set the shading model to unlit. you multiply the diffuse with the lightmap and done. dirt cheap static lit. hmm
just watched video on youtube about that I think that unlit emisive is solution, but then there is no metalness, and specular? how to solve that ?