Since the settings on this site don't save for everyone, I've decided to disable gifs at the browser level. In Firefox that means going to about:config and setting image.animation_mode to none. This disables it on all websites, which is good, because gifs get abused way too much. I'm guessing in Chromium you will need to install an extension.
On chromium the settings just work so an extension isn't needed. It's so weird that FF isn't persisting localStorage, which is the entire point of the feature.
I really think that has to do with Enhanced Tracking Protection. I used Floorp while Neolib uses Tor. I think both of those enable Enhanced Tracking Protection by default. It may not be an issue in upstream Firefox.