It's ridiculous. If you actually go into the science, you'll see that the Flat Earhers just have no understanding of math or science. They 'feel' like they live on a flat surface, and so everything they are promoting is merely confirming their bias. There are literally hundreds of easy disproofs of a flat earth.
In fact, if you actually understand their map, the 'best' map that FE'ers have created in thousands of years is an Azimuthal Projection Map of a GLOBE! And come on, flights go from Sydney to Johanessburg and fly OVER Antarctica! If the earth was as they say, these flights would be impossible, and they would crash into the side of the dome!
Just do the science. It's not flat.
Their arguments are ridiculous.