There is a quick hack you can use to get hCaptcha kind of working on MediaWiki 1.31-1.34. This is not an official backport—use at your own risk. I'm not liable for any potential security breach that may result from these changes.
- Change line 139
protected function addCaptchaAPI((as seen at https://github.com/wikimedia/mediawiki-extensions-ConfirmEdit/blob/master/hCaptcha/includes/HCaptcha.php#L139) to
public function addCaptchaAPI(.
- Remove the call to the addCSPSources() method on line 41 of
HTMLHCaptchaField.php, since pre-1.35 doesn't offer support for this (as seen at https://github.com/wikimedia/mediawiki-extensions-ConfirmEdit/blob/master/hCaptcha/includes/HTMLHCaptchaField.php#L41).