I have tested this on multiple devices, it seems youtube has broken their site on firefox for android. I can no longer fullscreen properly, it doesnt auto rotate. It defaults to the 244p resolution for every video, making me have to manually change the resolution everytime i want to watch something, It no longer allows the miniplayer or PIP, and you can no longer press play through the notifications widget as it no longer shows, thus not allowing us to listen to a video while minimized or on another tab. These features all work on other sites without issue which makes me think its a thing youtube did to circumvent adblockers. It's like this on my friends phone too it started at the same time.