I notice nobody has posted a helpful answer, it looks like there’s a few ways to handle this problem. The first way is a javascript bookmarklet that doesn’t like modern protections that stop javascript cross domains, but you can find it here: https://slbkbs.org/jsgif/ It seems to work on that page, and it needs the browser to be set to full screen to work.

There’s an addon on the extensions store, it needs a right click on every gif to open it in a new window and seems to work just fine: https://addons.mozilla.org/en-GB/firefox/addon/gif-scrubber3/

There’s also an addon that would need to be sideloaded, but I don’t know how good it would be. It seems to convert gifs into videos first, and needs a lot of work to get it going: https://github.com/brunoluiz/gifsane-extension

Finally there seems to be a website that will do the lifting for you, but it would need you to paste every gif into it manually: https://onlinegiftools.com/play-gif