Document Interface language vs. content language block

Problem/Motivation

I want to configure the language detection behavior to be different for content language and interface language.
Therefore I check the checkbox "Customize Content language detection to differ from Interface text language detection settings" on the language detection settings (/admin/config/regional/language/detection). For the Interface text language I configure the Users selected language (Follow the user's language preference.) to be top priority for language detection as the admins want to have the toolbar, edit forms and so on to be in the language they chose, so that they can understand every field and function.

For the content language detection, I choose URL (Language from the URL (Path prefix or domain).) to be the top priority.
But now the dropdown language switcher isn't working anymore to switch between different content translations and it doesn't show the current content language because it seems to be using the interface language instead of the content language.

Proposed resolution

Change the module code, so that the dropdown language switcher depends on the content language (which you normally want to change with such a language switcher) instead of interface language.