Finally, got it working properly using 4.13. I didn’t check 4.12.5 again, but tweaking Skylight parameters and baking in Production quality did it for me \o/ (although I don’t think I will be baking in that quality until I really need to check the overall final look - takes forever to bake)
Thanks a bunch folks !!!
The only issue I still have if the piece of sand dunes that protrudes inside the “crypt” - never gets dark
Also while I was experimenting with it, I got another question here: SkyLight - Capture Scene vs Cubemap - why so ... different ? - Rendering - Unreal Engine Forums
Thanks