Error trying to run a Flutter WEB app, using Firebase

I have a Flutter app, using Firebase, running just fine on iOS and Android (emulators and physical devices).

I'm trying to compile and run it for the web, and I get an error when trying to use Firebase services (specifically ConfigRemote but I suspect it's a Firebase general issue).

This is the first time I try to compile for web, with Firebase, so my knowledge here is quite limited...

What I've done:

1. Added a web app on the Firebase console
2. Copied the required scripts into the body tag (index.html)
3. Added all dependencies scripts (index.html)

     <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-app.js"></script>
     <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-firestore.js"></script>
     <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-auth.js"></script>
     <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-functions.js"></script>
     <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-storage.js"></script>
     <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-remote-config.js"></script>
     <script src="https://www.gstatic.com/firebasejs/8.6.1/firebase-messaging.js"></script>

The error I'm getting (at await ui.webOnlyInitializePlatform()):

Error: NoSuchMethodError: '<Unexpected Null Value>'
method not found
Receiver: null
Arguments: []
    at Object.throw_ [as throw] (http://localhost:64231/dart_sdk.js:5348:11)
    at Object.throwNullValueError (http://localhost:64231/dart_sdk.js:5314:15)
    at Object._notNull [as notNull] (http://localhost:64231/dart_sdk.js:5667:25)
    at new core.Duration.new (http://localhost:64231/dart_sdk.js:123963:168)
    at method_channel_firebase_remote_config.MethodChannelFirebaseRemoteConfig.new.setInitialValues (http://localhost:64231/packages/firebase_remote_config_platform_interface/src/method_channel/method_channel_firebase_remote_config.dart.lib.js:230:26)
    at Function.instanceFor (http://localhost:64231/packages/firebase_remote_config_platform_interface/src/method_channel/method_channel_firebase_remote_config.dart.lib.js:88:118)
    at firebase_remote_config.RemoteConfig.__.get [_delegate] (http://localhost:64231/packages/firebase_remote_config/firebase_remote_config.dart.lib.js:62:131)
    at firebase_remote_config.RemoteConfig.__.setConfigSettings (http://localhost:64231/packages/firebase_remote_config/firebase_remote_config.dart.lib.js:138:18)
    at _loadRemoteConfig (http://localhost:64231/packages/bla/main.dart.lib.js:299:26)
    at _loadRemoteConfig.next (<anonymous>)
    at runBody (http://localhost:64231/dart_sdk.js:39250:34)
    at Object._async [as async] (http://localhost:64231/dart_sdk.js:39281:7)
    at Object._loadRemoteConfig (http://localhost:64231/packages/bla/main.dart.lib.js:293:18)
    at main$ (http://localhost:64231/packages/bla/main.dart.lib.js:288:18)
    at main$.next (<anonymous>)
    at http://localhost:64231/dart_sdk.js:39230:33
    at _RootZone.runUnary (http://localhost:64231/dart_sdk.js:39087:58)
    at _FutureListener.thenAwait.handleValue (http://localhost:64231/dart_sdk.js:34073:29)
    at handleValueCallback (http://localhost:64231/dart_sdk.js:34633:49)
    at Function._propagateToListeners (http://localhost:64231/dart_sdk.js:34671:17)
    at _Future.new.[_completeWithValue] (http://localhost:64231/dart_sdk.js:34513:23)
    at async._AsyncCallbackEntry.new.callback (http://localhost:64231/dart_sdk.js:34536:35)
    at Object._microtaskLoop (http://localhost:64231/dart_sdk.js:39374:13)
    at _startMicrotaskLoop (http://localhost:64231/dart_sdk.js:39380:13)
    at http://localhost:64231/dart_sdk.js:34887:9