Install a family XMPP server like Snikket or otherwise. Show them the benchmarks of how little battery & data plan drain is used from Conversations forks. Explain how bloated Electron apps are & how you don’t wish that on your loved ones vs. Dino, Gajim, or a TUI client. Sidecar a Movim server so y’all can share long-lived, non-ephemeral posts instead of losing memories like photos in some long group thread. Let them know their data is safe with you as the operator instead of some massive for-profit corporation—and if they don’t trust you, they are empowered to start their own server to interop.
(This tactic has yet to work for me, but I will keep running into that wall til it breaks 😃)