And yet, nobody ever has a good answer for why the constellations are different in the North and South

Answers are easy. That's the purpose of virtually all mythology. What matters is if the answer is correct! There are answers available while assuming a flat earth worldview - however, it doesn't change the fact that attempting to determine the shape of what you are standing on by studying the complete opposite direction of it is both unscientific and incredibly stupid. You don't determine the shape of the floor by studying the ceiling...

why we don't have a picture of the edge.

Perhaps because no one has reached it. Perhaps because there is no edge to reach! In any case, we have pictures of the loch ness monster and ghosts...