ne fonctionne pas npx react-native init myapp - template react-native-template-typescript

There seems to be quite some confusion about the legacy CLI. 
This template only works with the new CLI.
Make sure you have uninstalled the legacy react-native-cli first (npm uninstall -g react-native-cli),
for the below command to work.
If you wish to not use npx
you can also install the new CLI globally (npm i -g @react-native-community/cli or yarn global add @react-native-community/cli).
Singh99