Signal is the world’s most widely used truly private messaging app, and our cryptographic technologies provide extra layers of privacy beyond the Signal app itself. Since launching in 2013, the Signal Protocol—our end-to-end encryption technology—has become the de facto standard for private commu...
My understanding is outdated but what I recall was mentions that Matrix leaks metadata like a government fund, and that it has the same issue Mastodon has of being “nu-tech”, protocols and systems being made too heavy, under the assumption that everyone has octacores with liquid nitrogen refrigeration and 32 GB RAM to run servers. In comparison, while XMPP is not as lightweight as IRC, you do can still run something like Prosody at marginal CPU usage cost.