The support page for link previews in Figjam states:
Figma will create an interactive preview if embeds are supported by the resource’s site. Otherwise, Figma will create a static preview.
… but specific requirements for how to ensure a URL is treated as an interactive preview are not included. From some investigation it appears that it is related to OEmbed and OpenGraph tagging on the page which is being added as a preview, but are there specific requirements anywhere so I can ensure compatibility with interactive previews?
Thanks!