Just allow it for youtube, while keeping everything else blocked. Whitelisting is the best option because there aren't that many websites primarily about playing video. Nobody goes to Youtube for other activities. Clicking a video link means you intend watching.
News websites are the worst. Clicking a news article means I want to read the article, not watch a video. If I want to watch the video on a news website (rare) I will press play. If they autoplay videos, I send them nasty angry feedback and don't return if I can help it.
Whitelisting is about the worst thing you could do. It makes any kind of competition and therefore inovation on the web impossible and under the vendor's control.
Simply ask the user to allow autoplay, same as you would with mic or camera permissions.
News websites are the worst. Clicking a news article means I want to read the article, not watch a video. If I want to watch the video on a news website (rare) I will press play. If they autoplay videos, I send them nasty angry feedback and don't return if I can help it.