Use case in D8: Front end in Spanish (ES), Admin page in English (ES). Front end Users register/login in Spanish and view menus in ES. Content Type create is in spanish and do not need translation, content fields to be translated. Admin users view all interface in English. There is no need for interface switch module.
I could set content language as ES default, but how can enable all admin users to login and view as English by default.
I could set /admin/config/regional/language/detection and have /es for all front end users. But, what about default front page which is not needed in English?