Content localization language switcher doesn't work

The content localization language switcher doesn’t work on my forum. It is visible, but when you select English, the result is still a German forum interface.

There is no hint in the description of content_localization_language_switcher that another setting is required for this to work. The supported locales are configured and show up in the dropdown. The content localization feature itself is enabled too.

allow_user_locale and set_locale_from_accept_language_header are also enabled.

Do I need to enable set_locale_from_cookie or set_locale_from_param? Or where is the problem in my configuration?

FAQ at Content Localization - Manual and Automatic with Discourse AI says yes.

I have read the topic. I think the question you mean is about automatic translation. How am I supposed to know which of the settings for “automatic translation” are also required for manual translation? Do I also need to enable AI translations for the dropdown to work?