The only reason anyone talks about Flat Earth theory is to stop people from looking into ring earth theory.
The fact is that the sky is an artificial projection. We have gone to space. The images are not fake. Our governments are not aware of the Ringworld. However, it is the true structure of our world.
If we dig deep enough into the ground, we'll encounter the artificial vacuum of space, not a molten core, not China.
A species of ape was deposited here millions of years ago; over time, offshoots developed intelligence, agriculture, metallurgy, militaries, economies. This was expected by the aliens who put us here, who are still in contact with various groups on the ground, having gone into hiding on artificial constructs across the galaxy, like our Ringworld but in many cases larger (i.e. Dyson spheres, O'Neill cylinders, etc. to survive a holocaust being perpetrated by another faction of beings from beyond our habitat (we ourselves, being aliens, are also simply a faction of beings).
The next X-Files season will feature a variation on Flat Earth theory to a) debunk dissident theories of terrestrial geography and b) draw attention away from Ringworld theory