Matrix 1.0 - Are we ready yet? We need your help to spread the word, tell your friends, your enemies, your acquaintances, people you sometimes see on the bus. Let's get going! https://matrix.org/blog/2019/03/15/matrix-1-0-https-arewereadyyet-com/
@nemesis this is fine. you're meant to put the server_name from @username:server_name into the tester, not the hostname from your client-server API path.
mastodon.matrix.org is one server in the network