How to expose the user's email on the user's detail page? Currently in the manage display page there is no way to display the email field in the manage display page. How do you expose this in Drupal 8 contacts details page?

There can be a work around for this as in user template or views-block rendering on profile page.
By default the mail field is not configurable in view modes.

You can change this in a custom module. Place this hook in mymodule.module

function mymodule_entity_base_field_info_alter(&amp;$fields, $entity_type) {
  if ($entity_type-&gt;id() == 'user') {
    if (isset($fields['mail'])) {
      $fields['mail']-&gt;setDisplayConfigurable('view', TRUE);
    }
  }
}


and you'll find the mail field in the Manage Display page.