Question Mark being added to amphtml

In the current stable version of the plugin, this is expected behavior for any hierarchical CPT. See my rationale from 3 years ago.

Nevertheless, in the next version of the AMP plugin (v2.1), we will provide the ability to have complete control of over the “Paired URL Structure”. See issue https://github.com/ampproject/amp-wp/issues/2204

The feature has been implemented in this PR: https://github.com/ampproject/amp-wp/pull/5558

If you want to test an 2.1-alpha pre-release build, you can access a build here: https://github.com/ampproject/amp-wp/wiki/Development-Builds

Also, it doesn’t matter to the AMP Cache what the AMP URL looks like. So functionally ?amp and /amp/ should behave the same way.

That makes sense but I am wondering why that one CPT is using /?amp and the rest are using /amp

I would like consistency across all of them. Are the settings stored in a file or the database for which method is being used for each CPT that I could edit?

Thanks!

CPT which is hierarchical gets ?amp whereas a non-hierarchical CPT gets /amp/. The full logic for whether to use a query var can be found here for your old version of the plugin: https://github.com/ampproject/amp-wp/blob/1.5.3/includes/amp-helper-functions.php#L416-L443