When you add a language in System → Languages, you’re telling the system which languages to prioritize for things like app text, date formats, and system UI if localization is available. But for keyboards, it’s a separate layer.
For French and Armenian, my guess is those keyboards were already installed as part of the default AOSP keyboard (or Gboard, depending on your setup). So when you added the languages, the system just said “oh, I already have those input methods available” and made them selectable.
Chinese is different because it’s not just a different alphabet — it’s an entirely different input method (pinyin, handwriting, stroke, etc.). AOSP usually doesn’t bundle Chinese IMEs by default, likely due to size and complexity. So when you add Chinese as a system language, the system can display Chinese text just fine — but it doesn’t automatically install a keyboard that knows how to type it.
So yes, you’ll need to install a keyboard app that supports Chinese input (like Gboard, Sogou, Baidu IME, etc.) and then enable it in Settings → System → Keyboard → On-screen keyboard. Once that’s done, you’ll see it appear as an option when you switch keyboards.
Nothing’s broken — GrapheneOS is just being minimal and not bundling large IMEs by default. Once you add the keyboard app yourself, it’ll work the same way as on regular Android.
Let me know if you want help picking a privacy-respecting Chinese IME or getting it set up!