A few corrections: - Matrix does not require you to host a server, even if I'd prefer it - there are multiple public ones in various jurisdictions. - There is XMPP - like Matrix, but older, jankier, much lighter and kind of freer. - Weird to call Simplex "centralized" if you did acknowledge that it's selfhostable... But it's indeed weird that last I've seen, there's not some directory with the public servers like there is for Matrix/XMPP. They seem to be going with adding other servers to defaults instead, like they did with Flux recently.