Create a custom field for a YouTube video url. This works for long and short video URLs that have v= or s= in them (use share links for shorts.) Sometimes the vid short links without s= will work as well.

Create a custom product field (in this case the code is youtube as you can see in the code below) that you put a YouTube video URL in.

Tip: Put a link to the product as the first comment after adding the video.

<mvt:comment>
#
YOUTUBE VIDEOS: We do some smt voodoo to control the embed via a URL posted in a product custom field

https://www.youtube.com/watch?v=7idtVo8vgDk
https://www.youtube.com/shorts/hnRUwY2azgc
https://youtube.com/shorts/hnRUwY2azgc?si=RwCP4aRiiEaIRHTJ

#
</mvt:comment>

<mvt:if expr="l.settings:product:customfield_values:customfields:youtube">
	<mvt:if expr="'v=' CIN l.settings:product:customfield_values:customfields:youtube">
		<mvt:assign name="l.settings:vid" value="gettoken(l.settings:product:customfield_values:customfields:youtube,'=',2)" />
		<mvt:assign name="l.settings:vid" value="l.settings:vid $ '&rel=0'" />
	<mvt:else>
		<mvt:assign name="l.settings:vid" value="gettoken(l.settings:product:customfield_values:customfields:youtube,'?',1)" />
		<mvt:assign name="l.settings:vid" value="glosub(l.settings:vid,'https://youtube.com/shorts/','')" />
		<mvt:assign name="l.settings:vid" value="glosub(l.settings:vid,'https://www.youtube.com/shorts/','')" />
		<mvt:assign name="l.settings:vid" value="l.settings:vid $ '?rel=0'" />
	</mvt:if>
	<iframe style="width: 100%; aspect-ratio: 16/9;" 
	src="https://www.youtube.com/embed/&mvt:vid;" 
	title="Treasures of the Southwest &mvte:product:name; video" 
	frameborder="0" 
	allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" 
	referrerpolicy="strict-origin-when-cross-origin" 
	allowfullscreen></iframe>
</mvt:if>