YouTube embeds and Error 153
As part of YouTube's TOS, the embedded player (i.e. iframe) must provide identification via the HTTP Referer header (not a typo unfortunately), otherwise you may end up with the following error:
To remedy this, make sure it's at least set to strict-origin-when-cross-origin. Adding referrerpolicy="strict-origin-when-cross-origin" to the iframe alone may not be sufficient.