I had earlier installed react-native-vector-icons in my Project and used the below command to link it:

react-native link

The “multiple commands produce” error seems is caused by the new autolinking feature in React Native 0.60 or above – the line use_native_modules! in ios/Podfile means when you do pod install, any pods found in node_modules are automatically linked.

So when you do pod install, links to all font files are added to [CP] Copy Pods Resources. If you previously installed react-native-vector-icons manually by adding the font files to Copy Bundle Resources, you then get a fatal build error similar to this:

Build system information
error: Multiple commands produce '/Users/xxx/Library/Developer/Xcode/DerivedData/Project-dcurwlhxaqikupbgxeiimmauwnpw/Build/Products/Debug-iphonesimulator/MyApp.app/SimpleLineIcons.ttf':

To fix the problem, remove the font files from Copy Bundle Resources, so that they are only in [CP] Copy Pods Resources.

In your Xcode, Select your Project and go to Build Phases and remove the fonts shown below from Copy Bundle Resources: