It’s possible to add a youtube video into a room by going to Build menu / Elements / Video. Builders canalter the floor of the video and paste in the youtibe link of a video.
Videos will autoplay once it enters the players viewport. When a player moves away, the video will keep playing in Picture-in-picture mode.
The playback is client side, so players won’t see the video at the same time as the other players in the room.