I have been researching JMonkeyEngine for a potential project and I noticed that there are tons of links out there in the ether that are hitting 404s for the old community posts.
A bit of minor URL experimentation, and I determined that if you (the hub site maintainers) were able to update your nginx configuration with the a redirect like the following, it would smooth out a lot of those old broken links!
(source: I am a web development professional going on 10 years)
rewrite ^/forum/topic/(.*)$ https://hub.jmonkeyengine.org/t/$1 permanent;
I hope that helps!