Instead, just sign up for a Matrix account via Element or another Matrix client, and then you can look at the Gitter server's room directory at Gitter.im and join its rooms from there. Because Matrix is one great big open network, you can pick any server for your account; you don't have to use the Gitter one :)
Will there ever be a way to show on gitter that a gitter account and a matrix account are the same person? I'm pretty active on gitter right now, and I'd like to choose a homeserver to have an account on so that my messages from the gitter client (logged in with gh) and the messages from a matrix client are from the same user. Would github login allow that?
Edit: also, what's the plan for private/invite-only gitter rooms?
There isn't really a plan for private/invite-only rooms but we could possibly support `virtualUsers` in the `sd.extraMembers`(security descriptor) field to allow inviting Matrix people to a private Gitter room.