Reproduce:

• Disable JavaScript
• View https://auth.wikimedia.org/test2wiki/wiki/Special:CreateAccount?useformat=desktop&usesul3=1&returnto=Main+Page&centralauthLoginToken=9370278a2691de5123020203010984fb

Expected:

• We should display "JavaScript is required to use create account form"
• The "Create your account" button should be disabled
• Even if JavaScript is enabled the "Create your account" button should be disabled until hCaptcha is loaded, so to prevent form being submitted without hCaptcha response

See also:
T378194: hCaptcha: Implement no captcha mode (API/no js usage)