It seems somewhat insane to have a cross platform approach and leave out the biggest platform of all, the web.
Or - looking at it the other way round - what approaches are there to take a working pwa website and turn it into an app? What advantages over such an approach can react native bring to the table?
It's currently the best maintained successor to PhoneGap/Cordova.
https://docs.expo.io/versions/latest/
Depending on the complexity of your app - expo is the best place to start with react-native. Their managed workflows allow you to write in 100% javascript w/ a lot of the native libraries already linked an exposed in JS. If you need something they haven't bundled already then you can eject and have a good starting point.
Expo web is still fairly new but they seem to have prioritized it as highly as support for Android and iOS.