CB

If only default language plugin is installed (en-GB default), but the Joomla selected language is en-US, then the default overrides don't override.
https://www.joomlapolis.com/forum/153-professional-member-support/244459-overrides-and-auto-actions#327044

Wouldn't it make sense that the overrides of the Default language be applied when the used language is not installed ?

And if not, then only if the dialect changes, but it's still the same (en) language, to still use the overrides ?