Simplex, element(or most matrix compatible messengers) session, bchat. If the goal is to get your family to switch over though good luck.
The topics and advice where wildly outdated and he didn’t want people starting at the beginning and taking advice that he has already matured passed himself or use procedures that just don’t work anymore.
Am I missing something I see a downvote button?
Matrix is a protocol that if used slows any messenger to communicate with each other kinda like lemmy federation. There are many messengers that use it and if you establish a bridge you can use your matrix client to message people on signal or what’s app