The best answer is Vinegar or acetic acid. Do not let anyone on this forum tell you hydrofloric acid. Hydrofloric acid will dissolve the WHOLE bone as well as the flesh.... and,,, LOL your mouth and teech when you bite into... wait... there would be nothing to bite into.... which is the entire point.
Soak your ribs in vinegar for a few days and the ribs will be soft enough to bite through. It will be nasty, and frankly I do not know why you would want to bite through the actual rib, but there you are. The meat around the rib will turn into mush though. The way this works... and its soooo brilliant... is because it ONLY dissolves the calcium, leavign the other materials behind... which of course, you will be able to bite through
I hope this was helpful.