How To Redirect Pinned Topic To External URL?

Sure, no problem.

  1. First go to the topic you want to have a redirect to external URL in;
  2. Create a post with whatever text you want along with the external URL;
    2a (Optional: If there is a graphic title in the external URL, you can Onebox the URL in your first post which will provide a visual aide to your external link.)
  3. Pin that post globally (it will always stay at the top of the lists of posts in that topic); and as an option,
  4. If you do not want/expect any new posts in that topic, Close the topic as well.

This way, you are not likely to break any links to the topic within Discourse, and you have your external URL always at the top when users go to that topic.
Edit: Pinning it globally should also keep that topic at the top of the list when a user clicks on “Latest” as well. :wink: