@webmind kindly recommended a bunch of non-Google captchas to avoid the Goog dependency (and possibly improve a11y):
QuestyCaptcha, mediawiki plugin we use for wikis. It depends a lot on
what kind of questions you ask. Questions which are simple but do
require some knowledge about the project seem to work best.
https://www.mediawiki.org/wiki/Extension:QuestyCaptcha
@webmind kindly recommended a bunch of non-Google captchas to avoid the Goog dependency (and possibly improve a11y):