SimpleX has no user account at all. No phone number, no username, no address book on a server. You connect by a one-time link or a QR code. Relays pass messages and are not supposed to learn who is talking. The apps are open source.
The network is small. Delivery can be slower than Signal. The person you want to reach has to be willing to scan a code instead of searching a name. That is the product. If a relay can be compelled, the design goal is that the relay has nothing useful: no graph of who knows whom. Treat that as a design claim you can read in their docs, not as a warrant-proof aura.
Use it when a phone number is already too much identity. Do not expect your family group chat to move. simplex.chat
SimpleX contacts are links. If you reuse one invitation everywhere, you built a public handle. Make a fresh link per person or per group. Relays are necessary and they are also a thing you can run yourself if you do not want the default servers. The app is the easy part. Getting one other person to scan the code is the deployment. Start with one contact, not a family announcement.
