react native doesn’t fill up window on ipad

Solution: In the xcode project, go to the general tab and then to the Deployment Info. There you can change to the device type you want (universal works for both).

If you are using Expo (create-react-native-app), modify to your app.json to set ios.supportsTablet to true:

"ios": {
    "bundleIdentifier": "your bundle identifier",
    "supportsTablet": true
},