I’ve shared this link to a category on our forum on Linkedin, and the preview looks like this:
I expected the image to default to one of the site logos, but that’s not the case - the pixellated image is my avatar, as the last editor of the category description.
The OpenGraph debugging page does show a site logo.
(Coin-coin le Canapin)
I’m not familiar with Linkedin. They have their own tool to preview links, though:
It shows this:
I don’t know what’s happening
If I had a guess to make, it would be that the issue comes from Linkedin and isn’t related to Discourse.