I watched the video you linked about the earth being flat. It's not that no one can debate that guy - it's just too much work. If we have to return to the most basic premises, then that's a philosophical debate. If the strategy of a debater is to outlast his opponent by making extravagant demands and more assertions than can be handled by one person, then the result will be that no one wants to engage in debate. That doesn't make him the victor - it makes him dishonest.

And frankly, flat earth is just lazy. There are very good alternative ways to explain the earth, which would be philosophically consistent with observation while not being materialist. I can and do regularly offer alternative explanations. That's not because I believe the alternative explanation, but rather because being fully sovereign requires the ability to invent my own language of metaphysic.

There is an easy way you can spot falsehood - just see if you can develop the model further. Reality is continuous ; communication, and thus models, are discreet. A perfectly accurate model would allow infinite detail - that's not possible, but you can apply the concept in the other direction. If a model has a cut off point, where further building is impossible, then its wrong. Flat earth is rationally wrong (rationally flat, lol) in probably an infinite number of ways, and failure to find any of these ways is proof of laziness.