Formula for a character’s height on a given frame of jump is h(f) = jf - 0.5g(f-1)^2 where j is initial jump force, g is gravity, and f is the airborne frame.
For jumps with frame 1 gravity active, simply change (f-1) to f. Get the x value where y=0, and round up to get the landing frame.
For jumps with fastfall, we can use q(f) = {h(f) | f < i}, {h(f) - m(f - i | f ≥ i} where m is fastfall speed and i is the frame on which fastfall is used.