First of all, the UIApplication.SharedApplication.OpenUrl(NSUrl url) was deprecated. But the OpenUrl(NSUrl url, NSDictionary options, [BlockProxy(typeof(NIDActionArity1V4))] Action<bool>? completion) is still supported. And Sanjay Hans used this method.
In addition, Maui has added OpenUrlAsync(NSUrl url, UIApplicationOpenUrlOptions options) api. You can use it:
await UIApplication.SharedApplication .OpenUrlAsync(new NSUrl(UIApplication.OpenSettingsUrlString), new UIApplicationOpenUrlOptions());