/tp @a "or" @e ~0 ~0 0 in command-block with hopper(two against each other) or comparator&redstone-torch(relatively fast(er)) clock, (2D world... ).

Only some of the teleportations, when walking or running while jumping, will send the player to the position that the player was in at the beginning of a jump. Possibly but not excluding when space was first pressed (and held) to jump, even when several jumps in a row and several teleportations in between the lag/reset thing were made.

With and without jump boost. Seemingly always 'to' a position on the ground.