Can you clarify exactly what you are attempting? I see no option to search the Apple website for any app keyboards. Why I try, I get no results and offers to open the App Store app.
Also, if you are asking about a specific keyword, what is the keyword? What are you looking for?
Or are you actually searching in the App Store? If so, have you switched your computer to French? You can't just add the language. You have to add the language, make it 1st in the priority list, and then restart.
The problem is that when you run "an app" like the App Store app, that is merely a front end. All Apple apps consist of multiple processes running in the background. So when you switch your language, or direct the system to run a certain app in a certain language, only part of it gets switched. For most 3rd party apps, this is no problem and they work fine. But Apple is different. You must restart for language changes to fully take effect.