Problems we are having with #Signal:
* It is and will remain centralized (clear strategy of *not* federating servers)
* It requires strong identifiers/selectors (phone#) to use
* Author disallows distribution by anyone but Google, although free/libre
* It keeps pushing away verification of fingerprint in interface
* It relies on Google+Amazon infrastructure
* Its funding is shady (OTF = Radio Free Asia = USG)
= clearly unethical choices, unjustifiable by accessibility or technological reasons.
So far it's looking good. Doesn't depend on a single server, even as a default. End to end encryption. Server and client are open source. They have a good track record on security, at least since NextCloud has become a mature product. Other than having to enter a server URL as well as a user name and password, it's pretty friendly to non techs to install and set up (excluding the server). Client is on FDroid.
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