Yeah, it is already hard to find reasons to use it for the average user, so people with disabilities (deafness, blindness,intellectual etc.) probably even have reasons to NOT use them (no subtitles, each instance might have different elements or structure that might be a nightmare for screen readers, it might be too complex for some people, etc.).
Wouldn’t Matrix be a better alternative to Signal, since it doesn’t need a number? Maybe it has a too difficult learning curve to the average user, though