Pour utiliser les extensions Android, vous aurez besoin de Firefox pour Android. Pour découvrir les modules complémentaires pour Firefox, veuillez visiter cette page.
Stylus is integrated on userstyles.org pages, it's the way it always worked. It's hard to guess what may be the problem in your case, but it could be another addon interfering.
We have a new feature in the works: https://github.com/openstyles/stylus/issues/243#issuecomment-348745988
