It kills the animation last I checked (a week ago). WebP animations work, even though they are restrictivr in quality. So for videos I convert a WebP preview and attach the source video.
GIFs worked for me a little over a week ago on !hentaigif but I haven't tested it super extensively. I generally also upload as WebP but that one was already a GIF so I didn't feel like converting it to WebP like I usually would.