The Signal messenger and protocol.

This is an interesting development. I wonder what third party platforms Facebook / Meta will approve. Maybe none. Maybe they're just trying to look good for the regulators.

As always, federated platforms are only as secure and private as their worst actor, which in this case will probably be something run by Mark Zuckerberg and co.

Personally, I don't think Signal should connect directly to Facebook platforms, but maybe I'm just cynical. Something Matrix-related might actually work better.