I’ve seen flat earthers claim the sun is small and close, and has a shade around the edges, which shades parts of the flat earth during nighttime. If that were the case, the shaded areas would still be light (the beam is smaller than what’s shown in this model). This doesn’t explain what we actually observe happening in real life in different parts of the world.

Only a distant sun with a spinning globe explains vertical time zones that always move in only one direction, and how the sun rises and sets.