I’m a bit confused about the image you shared…?
To my knowledge, Facebook “support” doesn’t even exist.
But this doesn’t seem to be a Facebook issue, because on my own Discourse installation, some images are shown, so I would just like to know what’s the process to make them work? Is the first image in the topic? If so, why would that topic from this very forum not work (along with others I tried), but for mine it did?
Maybe this will be a mystery to be unsolved.