Following Android getting started - 'Error loading page'?

1

So I followed Hotwire Native Android: Getting Started and I can see https://hotwire-native-demo.dev in the emulator, but when I change the URL at

    NavigatorConfiguration(
        name = "main",
        startLocation = "https://hotwire-native-demo.dev",
        navigatorHostId = R.id.main_nav_host
    )

to any other site, I just get ‘Error loading page’, why is that?