Did you know that Safari supports .mp4 videos in <img> tags for animated GIFs? https://developer.apple.com/documentation/webkit/delivering_video_content_for_safari/#3030249
Here is the historic context of the feature https://calendar.perfplanet.com/2017/animated-gif-without-the-gif/ and some unexpected consequences https://lapcatsoftware.com/articles/img1.html