Post #57: Godot Get Locale Language
When creating games, the audience size you are targeting matters. You can significantly increase your audience size (and make your game more user friendly) through having an internationalization plan.
This post doesn't go into how to do all of this well, but highlights one of the first building blocks: get_locale_language().
This function returns the OS language code, which you can then use to determine how you want to present your game, based on the language code being used.