In my books and videos you will find hundreds upon hundreds of proofs that Earth is devoid of any convex curvature, and the vast majority of these proofs double to show that Earth is also devoid of any concave curvature. For example, the natural physics of large bodies of water is to seek its lowest level with the surface of all standing water remaining perfectly flat from end to end of its container. Whether in a beaker, bottle or bathtub, pond, lake or ocean, this tangible substance which we can all confirm for ourselves, is incapable of supporting itself into any shape whatsoever. Regardless of what shape the ground beneath takes, the surface of standing water remains perfectly horizontal. This alone destroys the unscientific, unobservable, unrepeatable claim that Earth is a concave or convex ball.
The perfectly flat horizon seen for hundreds upon hundreds of miles at the highest altitude any amateur balloon, camera or human has ever reached, also shows beyond any shadow of doubt that Earth is not concave or convex. For Earth to be a ball of the dimensions claimed, means that it must curve (upwards or downwards!) at a rate of h = r - r cos(s/2r) where h = height, r = radius, and s = arc length. When calculated for up to nearly 1000 miles (which is plenty far for any practical observations we can make) this trigonometrical formula can also be simplified to 7.98 inches per mile squared and receive the same results. This means an easily visible and measurable curvature of 6 feet after 3 miles, 24 feet after 6 miles, 54 feet after 9 miles and so on would and must exist if we truly lived on a concave or convex Earth 24,900 miles in circumference. Countless experiments using lasers, spirit levels, theodolites, sextants, telescopes, super-zoom cameras, and Navy rail guns have all confirmed however that no such alleged curvature exists.
Again, there are hundreds more such proofs available in my other works showing the objective reality of our cosmology, so now I will specifically address the evidence given by concave Earthers to substantiate their belief that we are living inside a ball. The largest collection of concave Earth evidences I have been able to find, belongs to the Wild Heretic blog where he has amassed the following 10: https://ericdubay.wordpress.com/2019/07/11/concave-earth-debunked/