I must admit that I found the 'no curvature' video confusing, as I would not have expected that. Then again there are other aspects to consider such as the effect that one's chosen lens might have upon apparent curvatures - and since we 'may' be talking about a pretty large planetary diameter, it would not be too difficult for curvature to be imperceptible.

Maybe one way to resolve this matter would be for flat-earth believers to launch their own micro satellite into space?