Edit: the formatting seems to be the same as regular images, with the ! and [] and the link between (). I had no gif to upload so I used one that the keyboard app offered me. (I’m on Voyager)

Downloaded a gif. Trying to upload that gif:

Well, it works with Voyager. Maybe it’s your instance?

Edit again:

Your link as an embedded image with exclamation mark and without the text in the square brackets:

It doesn’t end with .gif, so does that even have a chance of working?