Explain how the setting sun, disappearing below the horizon, disappearing below the surface of Dubay's flat earth, doesn't ensure darkness all over the flat earth. Or shut up already.

That has not only been explained but demonstrated in action (in a small model at least) by many Flat Earthers. Besides that, you're attacking the Flat Earth from total ignorance based on this question. According to the FE model, the sun does NOT disppear BELOW the horizon, nor BELOW the surface. It stays above the surface the entire time. So you're attacking strawmen and things you have no comprehension of. And you continue to use ridicule and and the old "Dubay's flat earth" lie. Your dishonest tactics ae getting pretty old.