Lazy-load images on Youtube iframes

[arlg]

Is your feature request related to a problem? Please describe.
I'm using the feature to replace Youtube iframe by a preview image. I'd like this preview to have the "loading="lazy" attribute in order to lazy-load it on the browsers. This would satisfy PageSpeed tests.

Describe the solution you'd like
Maybe a filter or a plugin would be the right fit for this functionality ?

Describe alternatives you've considered

Additional context