Hold on, I'm gonna try something

Ok look at my profile again. I couldn't use your file because, as you pointed out, it's been converted to a webm, which doesn't give you as much options. For example, if you try to reconvert the webm to gif, it will lose its transparency (because of some complicated reasons I can't explain since I'm not a graphics expert).

So I went and found a gif just to use as an example. You can upload your gif to imgbb.com and then get the direct image link. Then use the ![] (image-link-here.gif)

markdown without the space I added between the brackets and parentheses. That should make the gif immediately visible when someone visits your profile (although it wouldn't be "the banner" per se).

One thing to note is that if you're using Jerboa, gifs never start autoplaying, so they have to be clicked. Afaik there's no way around that yet, but you could put in a feature request. I actually had a request once to be able to zoom images more due to my bad eyesight, and the devs came through, so they do take requests seriously.

BTW I'm only going to leave that gif on my profile until you have a chance to look, so please let me know once you've seen it. The reason being I'm actually a cis man, and it wouldn't be right for me to pretend to be something else. I just grabbed that as an example.