> When the flat-earth craze started I've been trying to at least get that bit actually personally verified. Haven't managed to do it to this day, though.

How do I say this in the most gentle way I can...?

Your brain is broke. No, seriously. If you can help it, try not to argue with anyone about anything, ever. You have a demonstrated inability to think clearly.

Your drive to verify must be very low then. There are hundreds of small logic reasonings or even experiments with which you can easily prove that a flat earth model is at least very complicated or even impossible.

Explaining Moon phases gets very complicated in any flat earth model. With binoculars you can see the shadows of craters on the moon's terminator. Or the phases of Venus whereas Mars doesn't have any.

Timezones are ridiculously hard to explain on a flat earth.

A proper theory must explain all of them and no flat earth model can do that. A round Earth OTOH easily does.