SMS
Nobody wants to use a messaging app at all. At this point I'd rather be stuck on WhatsApp. But its all family. Big family and try to get them to agree on anything is like pulling teeth.
I even sent everybody a "contact card" I made with my links to signal, simplex, and even whatsapp (figuring that's the path of least resistance) saying I'd prefer to communicate on any of those apps. ZERO people changed nor did they even ask about it, options, or my reasoning.