Not sure what you're expecting given how old it is. Why not write a polyfill as an exercise for yourself? Convert it to png, then save as an image tag to a data url.
It's always gonna be chicken-and-egg for this, and browsers won't spend the time sandboxing and supporting a codec until it's already popular.
So this will probably see a JS / Webasm shim, and if that proves popular, Blink and Gecko will consider it.
The day might come soon when browsers just greenlight a webasm interface for codecs. "We'll put packets in through this function, and take frames out through this function, like ffmpeg. Other than that, you're running in a sandbox with X MB of RAM, Y seconds of CPU per frame, and no I/O. Anything you can accomplish within that, with user opt-in, is valid."
Here look some people adapted to ios in one hour faffing around on twitch: https://www.twitch.tv/videos/1241476768?tt_medium=mobile_web...