Confusion integrating react-native-firebase with Expo - firebase

Question

I'm new to React Native development, and I'm making a development environment for a cross-platform app I'm building with Expo and Firebase.
I'm trying to integrate react-native-firebase with Expo because it's the only way I can use Firebase's 'App Check' functionality. I want a managed workflow where I'm not having to touch native code and am using the EAS development build.
I've tried to set up my environment using the following article, but it's left me confused about something - how do I connect my app to firebase? Do I use the standard web JS SDK, or is there something else I should be using?
I've looked at the react-native-firebase docs concerning the expo, which hasn't helped.
What's also confusing is this: when I was trying to add firebase to my android app on the firebase console, it mentioned adding the firebase SDK to a build.gradle file - something which my project doesn't have. So have a missed a step in my setup?
If it's any help, here are the steps I've taken for my project so far:
1.) Created app with npx create-expo-app
2.) npm install -g eas-cli
3.) npx expo install expo-dev-client
eas build
4.) npx install #react-native-firebase/app
5.) Set up a project on firebase. Download google-services.json and GoogleService-Info.plist, and add them to the root of my expo project
6.) Configure app.json as follows:
"ios": {
"googleServicesFile": "./GoogleService-Info.plist",
"supportsTablet": true,
"bundleIdentifier": "com.******.testapp"
},
"android": {
"googleServicesFile": "./google-services.json",
"adaptiveIcon": {
"foregroundImage": "./assets/adaptive-icon.png",
"backgroundColor": "#FFFFFF"
},
"package": "com.******.testapp"
},
"web": {
"favicon": "./assets/favicon.png"
},
"plugins": [ "#react-native-firebase/app"],

Answer 1

Gradle is a build tool commonly used for mobile application projects. However as you are using Expo, Expo is your build tool rather than Gradle.
In your app.json file, you can see that the configuration there mentions ./GoogleService-Info.plist and ./google-services.json. These are the configuration files produced by the Firebase Console once you register your iOS and Android applications.
They can be redownloaded following these directions.
Go to your Project settings in the Firebase console.
In the Your apps card, select the bundle ID/package name of the app for which you need a config file.
Click the download link for GoogleService-Info.plist or google-services.json (as appropriate).
Save the file to the root of your project, making sure that you only have the most recent downloaded config file.