There is no need to add extra code and no need to use AV player also. we can achieve that by initialising UNNotificationAttachment with url which we get after URLSession.shared.downloadTask
URLSession.shared.downloadTask(with: attachmentURL) { url, _ , _ in
let attachment = try UNNotificationAttachment(identifier: "identifier", url: url, options: nil)
content.attachments.append(attachment)
}
While updating the content in NotificationServiceExtension. Notification will load the video if it is video url.
Note: - please make sure video should be small size or as suggested by Apple.