Desert of Kharak might be using marmoset light engine and using PBR. We used the same in our project. There's also the possibility of using Autodesk Beast.
At the studio we have people that also worked in projects using Unreal 4 and its indeed more powerful. Shaders can be completely customized in UE4. Plus you can also use Blueprints to have full control on them. I base this on my knowledge with both engines. Our experience with Unity was awful.
Its a good engine but not appropriate for certain game types, that's all. Power wise its very limited when compared with how Unreal works. here I'm talking about pipeline wise.
And obviously we have access to all the latest versions of both Unity and Unreal.