No 404 when not using a language

Hello,

This plugin is not about SEO but rather about offering better experience to your end users, so things such as your request are out of the scope of what we do.

I really don’t see the why you will need to disable a language previously enabled, and remember that there are canonicals that you can use and the rel alternates are served.

You can add the rules in your .htaccess to return a 404 when a specific url matches.

Good luck