I ve had a similar issue, its due to volumetric lighting being forced in the TODM, even if you don’t see it in UEFN. Turning the TODM manager to off fixes the issue, but all the nice optimizations of FN go away with it, so we need a way to turn it off with the fn TODM active.
The black ceiling is again a TODM issue out of our control, FN creates shadows when normal tangents are not aligned or when there are planes (meshes) and there is no setting to turn it off. Again, it goes away if you turn off the TODM manager in world settings.