[@TheRedWatcher] That's why I said "assuming total deafness". If they're hard of hearing or deaf in one ear that's fine.

The sign language is fine as well but then you run into the other issue of who else is actually going to know the sign language? By its nature is a rather niche thing with a very specific use. Knowing sign language isn't going to help when most of the people you need to communicate with can only see it as hand gestures.