If you're already one of them, you can upload files in GIF format. But keep in mind that you can crop images after uploading them, but you can't crop GIFs. If I make my profile banner a gif, it appears animated in the preview, but as soon as I save the changes, it becomes static. Sometimes, the Discord server considers the gif as an image when it is loaded from the camera roll, so uploading it as a file solves the problem.
Turning on the option “automatically play gifs when possible” fixed the issue for desktop and Android users. But for many users, a poor internet connection causes the gif to not load properly, and the Discord server gets a damaged gif file that it can't play. In that case, instead of uploading gifs from the gallery or internal storage, use a gif app like GIFY to upload or share gifs. Please note that this is a different size than the standard 1920 x 1080 server banner that mods can use to set up a new Discord server.
Turn on “Automatically play gifs when possible” in the Discord settings to automatically play gifs. Open GIPHY and search for the GIF you want to edit, or tap the plus button at the bottom to access the GIFs from the camera roll. In some cases, your profile doesn't sync correctly with the Discord server, so gifs don't work or upload and cause problems. If, for some reason, the gifs don't play if you upload them from the camera roll, try uploading the gifs as a file.
If you're trying to upload a gif as an avatar, make sure you have at least one Discord Classic subscription. To fix Discord gifs not working, you can turn off Reduce Motion from iOS settings if you're an iOS or iPadOS user.