Flat-earthers as a significant portion of anything are a historical myth cooked up in the 19th century. Those who invoke them are historically ignorant. There is a great book out there entitled “Inventing the Flat Earth” by Jeffery Burton Russell. Prior to the 19th century in the west, there are at most 5 documented individuals who may have held that the earth was flat, though in the majority of these cases the evidence is ambiguous. The one really clear case is a guy in the 2nd or 3rd century who was condemned as a heretic (though for reasons other than his geography—his theology was as bad as his natural science). His Latin was really good, though, and he was widely read in the renaissance.
The flat Earth myth is so widespread there is no hope. I hear pastors regularly make reference to it and when I ask Christian church people everyone accepts the myths. No wonder because they are still in textbooks and repeated as common sense fact everywhere. Drives me crazy but then this current generation is as ignorant as any other in history about history and reality.