> It seems to me that speaking to a large number of people anonymously is not possible with 
  > any of the existing tools, Signal included

While it's still at the testnet stage, I have very high hopes for Maidsafe's SAFEnet. This will allow a completely anonymous internet, providing both users and publishers complete anonymity. Upon release of the actual network, it will live in the wild, just like bitcoin, with no company in control of it. Maidsafe's business model is to be one of many developers that will consult to companies who want to migrate their data storage onto the network. The network itself will be controlled by nobody.

It's peer to peer, but there are intermediate nodes which isolate content storage from those who view it, so neither IP addresses of storage nodes nor IP addresses of content consumers can be determined. Since there is no centralization, there's nobody for state actors to attack, legally or by force. All traffic is encrypted and even the ports are randomized, to avoid state firewalls from determining what the traffic is and blocking it.

I think it's our best hope to distribute large amounts of data to the world and avoid the censorship that many countries already have and that even those of us in the west see looming upon us.

You can learn more about it at https://safenetwork.org/ and https://safenetwork.org/documentation/ and https://safenetforum.org/