We're aware of issues that are impacting the ability to embed content when making posts. The team is working to have these issues resolved as soon as possible, but in the meantime, you may continue to notice that content will not be embedded properly on the Boards.
Additionally, if you plan on making a thread during this time, you will have to leave the "Link" section empty; otherwise, the post will simply show a loading indicator and not post.
I'll be updating this post with more information as I get it. Thanks for your patience!