...but the curve is going the wrong way in that video!

The options were flat or spherical, now you've gone and complicated things by offering evidence for a concave earth.
If you understood simple photography, a wide-angle lens can create that kind of curvature. However, proving any information to a flat-earther is nearly impossible if not impossible. If you send one on a rocket into space and tell them to look out the window, they will say the windows are screened/faked with a display. If you put in a spacesuit into space, the glass on the spacesuit or they have been drugged.
Fish Eye Lens: