You can add your own language to the app from App/Common/Languages.js
And reset the default from App/Components/RootRouter.js, this will move to the setting config on later version
The the language to Right to Left support:
Change the config RTL=true like the screenshot, you need to select the Default language from the Language file.
You could see the RTL is loaded correctly but the datetime is not changed, let's go to Components/Custom/react-native-timeago to uncomment link this screenshot.
On ios you need to change the plist like this screenshot: