How does one connect to users on WhatsApp and Messenger from outside of Meta?
You mail them a fucking letter saying, "Leave meta."
You call them on the phone and say, "Leave meta."
You visit them in person and say, "Leave meta."
Hack into a defunct spy satellite and carve "LEAVE META" in the countryside using its lasers.
People exist outside of meta. They breath, they eat, they shit. Find that pile of meat that exists outside of zuck's servers and get a message to it.
Shit, how did people communicate before facebook?