I watched this video
I want to download the same app, the video was just a few months old. However, I could not find the app.
My location is US.
I searched the package name of the app you are talking about is
com.google.android.apps.inputmethod.cantonese I didn't find any thing on play store There might be 3 reasons for it
-> The app is not available in your region
-> Your device does not support the App
-> The App was unlisted from playstore
the first option seems more likely
Any way you can always download the APK from external sources , might not be the safest but it works