let userAgent = 'Mozilla/5.0 (iPhone; CPU iPhone OS 12_0 like Mac OS X) AppleWebKit/ 604.1.21 (KHTML, like Gecko) Version/ 12.0 Mobile/17A6278a Safari/602.1.26';
if (Platform.OS !== 'ios') {
  userAgent = 'Mozilla/5.0 (Linux; Android 8.0.0; TA-1053 Build/OPR1.170623.026) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3368.0 Mobile Safari/537.36';
}
return (
  <SafeAreaView>
    <WebView
      ...
      userAgent={userAgent}
      ...
    />
  </SafeAreaView>
);