maui: Blazor startup not working on Android

Description

Based on the documentation in order to call C# backend from BlazorWebView we must wait for Blazor initialization. On Windows mode it is working as expected. But on Android the following exception is thrown:

[chromium] [INFO:CONSOLE(1)] "Uncaught (in promise) TypeError: window.external.receiveMessage is not a function", source: https://0.0.0.0/_framework/blazor.webview.js (1)
[chromium] [INFO:CONSOLE(1)] "Uncaught (in promise) Error: Blazor has already started.", source: https://0.0.0.0/_framework/blazor.webview.js (1)

Please fix it as the MAUI is not working on Android. So at least I am not able to start the app as in my case a call to backend is required on startup.

Steps to Reproduce

1. Clone the repo: https://github.com/fairking/MauiApp1.git
2. Open the project in VS
3. Run in Windows Mode, you will see the following message: “Hello World OK!”
4. Now run in Android Mode, you will see the following message: “Loading…” and VS output will log the errors mentioned in the description above.

Version with bug

6.0 (current)

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

Android 9.0

Did you find any workaround?

No 😦

Relevant log output

[chromium] [INFO:CONSOLE(1)] "Uncaught (in promise) TypeError: window.external.receiveMessage is not a function", source: https://0.0.0.0/_framework/blazor.webview.js (1)
[chromium] [INFO:CONSOLE(1)] "Uncaught (in promise) Error: Blazor has already started.", source: https://0.0.0.0/_framework/blazor.webview.js (1)