If the world was flat, would it be possible to see Mount Everest if it was on the other side of the Earth on a clear sunny day?

Well, no, not from everywhere on Earth, my friend. As many people have pointed out in the comments, the atmospheric gets pretty thick at distances comparable to the distance obscured by Earth’s curvature. That's why flat earthers love to harp on that point.

And yes, at that distance, the haze prevents line of sight too. But we know the curve exists in many other ways.

OP: “If the world was flat, would it be possible to see Mount Everest if it was on the other side of the Earth on a clear sunny day?”

Why do people hate on Serena (anime character)? What did she ever do to anyone except be a good friend to Ash Ketchum and an awesome trainer herself?

If the Earth were flat, you would think the telescope on top of Muana Kea should be able to see Everest. It can't. It can't see Mount Shasta in California. It can't even see Kawaikini on Kauai. It cannot see another mountain top more than 280 miles away because the Earth is a sphere.

And you cannot see the top of Everest from the surface more than 280 miles away either, because the Earth is a sphere.

You cannot see farther than about 280 miles across the surface. Ever. No matter how hard you try. The only way, and I mean ONLY way to see farther than 280 miles is to fly.

Mariners fall flat again: 'We'll keep fighting' - The Seattle Times

And if you can see farther from the air, why can’t you do it on the ground??