This is my regression which I will get fixed, it is due to:
https://github.com/discourse/discourse/commit/3015030fe21a120f42aadcdd14e84cb3e964f873
In the past we used to run all requests to unlisted topics via the “auto correct slug” logic, this was a security hole allowing users to simply guess the URL of unlisted topics. Now we expect the slug to match exactly for unlisted stuff.
Somehow clicks from the front page are relying on the redirect logic, which is a performance issue anyway.
workaround is to delete the /2 at the end of the URL and refresh but I will fix properly.