Is not possible enable this slug? /amp/ on the end URL? I believe that would solve my problem.
Since you are using the plugin in Transitional mode the ?amp
query var is currently the only one available (The other user’s URLs are in Reader mode). I also believe the Newspaper Theme’s templates automatically configure this mode of the plugin.
In a future release, all urls will be using the query parameter by default, but with the possibility of being customized. See the following: https://github.com/ampproject/amp-wp/issues/2204
Note that the Googlebot will eventually reindex your new URL structure. We cannot provide a timeframe (Search Console Help is the best resource for search questions), but since you have the appropriate links in the source code of your AMP and non-AMP URLs that indicates where the correct version resides.