Can just use avif instead, it holds an AV1 stream and acts like gifs/images do WRT looping — also very broad support (more than AV1 in WebM containers).
Demonstration:

Edit: switched to an example with simpler decode requirements.
Can just use avif instead, it holds an AV1 stream and acts like gifs/images do WRT looping — also very broad support (more than AV1 in WebM containers).
Demonstration:

Edit: switched to an example with simpler decode requirements.