If you get the signup loop, try this:
- Close all Wikimedia Space and Phabricator tabs.
- Restart your browser.
- Go to https://discuss-space.wmflabs.org/ and click "Sign up"
- If you still get the loop, try "Log in"
If nothing of this works, you can create your account using your mobile phone (no problems reported so far).
Once you have your account created, you can "Log in" to Wikimedia Space from your desktop (no problems reported so far).
At https://discuss-space.wmflabs.org/, clicking "Sign up" or "Log in" starts the authentication process with Phabricator. In some situations, this process enters a loop after clicking on "Continue to Application", giving a brief flash of the Discourse registration screen, but then returning to the Phabricator page.