The folks I have convinced to start using Telegram are not tech savvy at all. They just want to contact me through something like whatsapp. If people don't want to install it (a couple of seconds of work) - and those people indeed exist - I just text / mail or phone with them.
Yappari was great and maybe can start working again, but ceene needs to decide for himself if it is worth the effort. Even after he fixes the current issue, nobody knows what Whatsapp will do with their codebase next year.