I have a site setup for multiple languages, and for installed languages it works correctly. I have no need for the languages on the backend/admin, just for content on the front-end. So I added a Content Language for Spanish Castellano. There is no "official" language pack for this language.
For all of the other languages, the site detects (via url) the language, and then uses the proper menu/articles/modules/etc. For this content language, it ignores the language code in the url and returns "Category Not Found".
For example, the following urls work correctly:
But if I use the code for the Content Language (es-cn), it keeps the current language code. From a French page, if I enter:
Any ideas on how to get Joomla 3.8.x to respect/understand the sef language code for a Content Language?