Start with yarn start in one terminal and yarn ios in another. Then press the Go button in the app.
When the button is pushed I get the following warning in the console:
Require cycle: node_modules/react-native/Libraries/Network/fetch.js -> node_modules/whatwg-fetch/dist/fetch.umd.js -> node_modules/react-native/Libraries/Network/fetch.js
Require cycles are allowed, but can result in uninitialized values. Consider refactoring to remove the need for a cycle.