I searched for several hours to implement firestore offline persistence because its crucial for my app to work. I handle multiple chats inside my app and its a fatal error to download data every time again.

This is my code sample, its the root App.js file which is the first one beeing called:

....
//imports related to firebase
import * as firebase from "firebase";
import ApiKeys from "./constants/ApiKeys";


export default function App() {
  //firebase project initialisation
  if (!firebase.apps.length) {
    firebase.initializeApp(ApiKeys);
    var db = firebase.firestore();
    db.settings({ experimentalForceLongPolling: true });
    console.log("DB INITIALISED");
    db.enablePersistence() //HERE IS THE PROBLEM
        .catch((err) => {
            if (err.code == 'failed-precondition') {
                // Multiple tabs open, persistence can only be enabled
                // in one tab at a a time.
                // ...
            } else if (err.code == 'unimplemented') {
                // The current browser does not support all of the
                // features required to enable persistence
                // ...
            }
      })
  };.....

The API Keys look like this:

const firebaseConfig = {
    apiKey: "***",
    authDomain: "***",
    databaseURL: "https://***",
    projectId: "***",
    storageBucket: "***",
    messagingSenderId: "***",
    appId: "***",
    measurementId: "***"
  };

  export default firebaseConfig;

I receive the following error which I can not work around:

FirebaseError: You are using the memory-only build of Firestore. Persistence support is only available via the @firebase/firestore bundle or the firebase-firestore.js build.

I have installed the complete "firebase" bundle and also access to @firebase/firestore, I checked this already, and I implemented it same as in the official docs. Everything works but when I want to enable the persistence... It crashes with the error mentioned above.

What can I do now? Do I miss another package, have I done something wrong?

As a sidenote, authentification persistence works perfectly inside my app, just the firestore persistence is failing.

Currently using firebase SDK 8.2.3