It actually is enabled, just a bug with the single sign-on which should be worked out soon. For now, click on Sign in and then you will be able to create an account.
You mean "Sign in with single sign-on"? Because right now the flow is
- Go to https://chat.mozilla.org/#/welcome
- Click on "Sign in"
- Options are "Sign in with single sign-on" or "Create account"
- "Create account" fails with "Registration has been disabled on this homeserver."
So if I "Sign in with single sign-on", I create an account, but if I "Create account" I can't?