How to display the user's preferred language in a User profile page In a Drupal 8/9 site, I can select the User's preferred language.
In the &quot;Manage form display&quot; page (for user's fields), there are two rows which are about language:

Language settings (settings = --no settings available--)
Language code (settings = &quot;language select&quot; as the only option)

Question 1 : What do these two options produce?
In the &quot;Manage display&quot; page, I can display only one item about the language : Language code
As a result, if I visit my user profile page, I can see:

Language code: French

But if I change my preferred language in my user edit profile page into Dutch, there is no effect in my &quot;User view&quot; page: it is always &quot;French&quot;
ok, I can preprocess something and adapt the twig template to display my preferred language but this is not the answer I would like to have.
Question 2: I would like to understand this behavior because, as always in Drupal, I am sure there is a good reason for that.
I think I could answer myself to most of my questions:
1-The Language code field store the initial language of a user... it looks like it can't be changed after all. For my use case, it is an useless field.
2-The Language settings options display the Preferred language widget and the Administration pages language widget. I think that this last widget is there only if you check Account administration pages language setting. in admin/config/regional/language/detection
3-The most important part: How to display the preferred language of a user in the the display user page (/user/xxx)
You can do it with this hook:
function mymodule_entity_base_field_info_alter(&amp;$fields, EntityTypeInterface $entity_type) {
  if ($entity_type-&gt;id() == &quot;user&quot;) {
    $fields['preferred_langcode']-&gt;setDisplayConfigurable('view', TRUE);
  }
}

I really don't know why it is not a default... (don't hesitate to add any information on this point)