Also, this is a good tip in general:
You can't fetch title and thumbnail for YouTube links that starts with youtu.be
. This applies not only in Lemmy, but other websites too, for example Twitter (even before Elon's era).
This is, IMO due to the link doesn't really contain HTML and OpenGraph metadata. It only redirects you. If you try cURL-ing the youtu.be link, you will see that it doesn't have a response body, only some header including Location
header that will tell you where to redirect. The response code itself is 301.
My Lemmy instance actually can't fetch YouTube thumbnail, so I actually have to put it manually lol.
See http://www.get-youtube-thumbnail.com/