For people looking for a guide on how to set up a modern XMPP server, take a look at the homebrewserver.club #howto:
https://homebrewserver.club/configuring-a-modern-xmpp-server.html
It was updated at the recent Dusseldorf XMPP sprint.
Why is this step necessary? mastodon.sdf.org might not be the server where you are registered, so we need to redirect you to your home server first. Don't have an account? You can sign up here
mastodon.sdf.org