[BUG] WKWebView URL not loaded when called from MainThreadScheduler

[vincentSerrano]

Describe the bug

Hello !

I've got a desktop app (Windows and MacOS) using ReactiveUI
The scenario I'm trying to implement:
Display a modal Window (which display a WebBrowser / WKWebView) when my business logic fails.

• Everything work as expected with WebBrowser on Windows.
• But on MacOS, I've got an issue: My WKWebView doesn't seems to load URL: My Window is displayed, but it stays black.

Does anyone can see what's going wrong with my implementation ?

Thanks in advance !

Implementation details:

public static void ReproduceIssue()
        {
            Observable.FromAsync(DoBusinessLogic).
                ObserveOn(RxApp.MainThreadScheduler).
                Subscribe(
                    _ => { },
                    OnBusinessLogicFailed,
                    () => { });
        }
...
private static void OnBusinessLogicFailed(Exception e)
        {
            var nSWindowController = CreateWindow();
            _ = NSApplication.SharedApplication.RunModalForWindow(nSWindowController.Window);
            nSWindowController.Close();
        }

Steps To Reproduce

Repo: https://github.com/vincentSerrano/RuiWebKitViewIssue

Expected behaviour

I expect the WebKitView to display the URL content.
Screenshots

RuiIssueRepro

Environment

• OS: macOS
• Version 11.5.2 (20G95)
• Device: MacBookPro16,1
• ReactiveUI Version: 16.2.6

Additional context