I found a workaround, maybe someone will have something more elegant then this:

private void webView21_CoreWebView2InitializationCompleted(object sender, Microsoft.Web.WebView2.Core.CoreWebView2InitializationCompletedEventArgs e)
{
    webView21.CoreWebView2.SaveAsUIShowing += CoreWebView2_SaveAsUIShowing;
}

private void webView21_NavigationCompleted(object sender, Microsoft.Web.WebView2.Core.CoreWebView2NavigationCompletedEventArgs e)
{
    webView21.CoreWebView2.ShowSaveAsUIAsync();
}
private void CoreWebView2_SaveAsUIShowing(object sender, CoreWebView2SaveAsUIShowingEventArgs e)
{ 
    e.AllowReplace = true;
    e.SuppressDefaultDialog = true;
}