public partial class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();

        this.richTextEditor.Loaded += OnRichTextEditorLoaded;
    }

    private void OnRichTextEditorLoaded(object sender, EventArgs e)
    {
#if WINDOWS
        var editor = (RadRichTextEditor)sender;

        var webView = FindDescendant<WebView>(editor);
        if (webView == null) return;

        if (webView.Handler?.PlatformView is WebView2 webView2)
        {
            webView2.CoreWebView2Initialized += OnCoreWebView2Initialized;
        }
        else
        {
            webView.HandlerChanged += (s, _) =>
            {
                if (((WebView)s).Handler?.PlatformView is WebView2 wv2)
                {
                    wv2.CoreWebView2Initialized += OnCoreWebView2Initialized;
                }
            };
        }
#endif
    }

#if WINDOWS
    private void OnCoreWebView2Initialized(WebView2 sender, Microsoft.UI.Xaml.Controls.CoreWebView2InitializedEventArgs args)
    {
        var webView2Profile = sender?.CoreWebView2?.Profile;
        if (webView2Profile != null)
        {
            webView2Profile.PreferredColorScheme = Microsoft.Web.WebView2.Core.CoreWebView2PreferredColorScheme.Light;
        }
    }

    private static T? FindDescendant<T>(IVisualTreeElement parent) where T : class
    {
        foreach (var child in parent.GetVisualChildren())
        {
            if (child is T match) return match;
            var result = FindDescendant<T>(child);
            if (result != null) return result;
        }
        return null;
    }
#endif
}