>The idea that people in recent history believed in a flat Earth is a myth.

The way you've worded this, you're incorrect. There are people today who believe in a flat Earth, crazily enough.

Of course, the idea that most of society (namely educated people) believed in a flat Earth is a myth. From your link:

"The myth of the flat Earth, or the flat earth error, is a modern historical misconception that European scholars and educated people during the Middle Ages believed the Earth to be flat."

What the typical serf working in the fields thought about the shape of the Earth is probably unknown.

If we had to guess (of course not good research to be guessing): The typical person working on a field probably believed what the church told them the world looks like. If they ever heard about being on a sphere, they would probably laugh and point to the horizon, saying: "How can Earth be a sphere? Don't you have eyes to see? Look into the distance, all is flat!" and any kind of argumentation, that it is simply so huge, that one cannot see it, would seem to them like a made up story, a lie to further some hidden agenda the explaining person has.

That does not really detract from my comment though. Thousands of years are also hundreds of years. Just more hundreds. So if we are getting technical about that, I don't think it is wrong what I wrote. Still, thanks for putting the time frame a bit clearer.