On YouTube

1. Open the video
2. Click the share option
3. Click the Embed option
4. Enable privacy mode, to prevent tracking cookies
5. Copy the code, it looks like the one below
6. Then add ?rel=0 behind the url to prevent it to load related video’s from other channels.
7. loading=”lazy” is a WP 5.7 setting to lazy load iframe embeds.
   

Example:

<iframe width="560" height="315"
src="https://www.youtube.com-nocookie.com/embed/W7orPvGlEJE?rel=0"
loading="lazy" frameborder="0" allow="accelerometer; autoplay;
encrypted-media; gyroscope; picture-in-picture"
allowfullscreen></iframe>Code language: HTML, XML (xml)