I've posted it before, I'll post it again:
https://youtube.com/watch?v=eeWWD9Rk5Qk
During sunset the sun disappears below the horizon and reappears during sunrise. When you have a sunrise in one place on Earth you have sunset on another place. This is only possible on oblate spheroids or similar shapes, it's IMPOSSIBLE on a "flat earth" where the sun could never fully disappear and would have to be visible from different distances on ALL locations at the same time. That's why we have timezones, summer in one place, winter in another, etc.
"Flat Earth" ignores 75% of the planet. Hell... 10p itself has so many locations all over the world, if the Earth is flat all must be training at the same times. You have so many possibilities to contact each other amongst 10p and yet you don't do it.