I don’t actually have an iPad, only iPhone. But if you give me a couple of hours I will do so and reply to your comment with my results
I did try on my iPhone and it didn't appear to work :(
I tried it on mine as well and it didn't work.
The API is at the same state across all versions of Orion as far as I can tell, which means that at the point it works on your iPhone it will also work on iPad. I would guess that it will be quite soon considering even a couple of weeks ago uBlock didn't work 100% and now it is fully functional.
https://github.com/WaldiPL/playbackSpeed
https://addons.mozilla.org/en-US/firefox/addon/playback-spee...
And let me know if it works on say a youtube video with speeds above 3x?