I have pasted some urls which don’t list any card option, why?
welcome to Coda Community!
It would be really helpful if you could share your example in your post (through the Share red button on top right, then you choose “embed”): this could explain better your issue, which is not totally clear (at least, not to me…).
has a card
but this one doesn’t
Ok, it depends on whether the web preview is available for that URL or not.
It is not a matter of Coda.
And not even of Discourse itself (this discussion platform), but please, have a look here if you want more information: https://meta.discourse.org/t/rich-link-previews-with-onebox/98088.
Thank you for the usefull link.