I don’t know if they were supported in 2018 as said here Allow direct import of animated gifs for sprite animations, but they are not now and I just noticed.
I tried to use a GIF image as a tiled sprite, but no GIF even appeared in the selection window, dragging it from the file manager to ‘Select an image’ didn’t work either.
Tried the same as a normal sprite, same result.
I tried again just to be sure, nope!
The current version of GDevelop doesn’t support GIF sprites and but should IMO.
EDIT: I’ve found that I can import animated GIFs by creating a new animation then importing a GIF image from piskel why can’t GDevelop’s UI do that?