Steps to dupe:
Open a browser
Go to: https://www.flyertalk.com
On the top section, there's the Hamburger icon, Magnifying glass icon, News, and Forums sections.
Click the Forums, it expands a big blue section.
Click All Forums

Get Page not found error (which seems to try to take you to: https://www.flyertalk.com/forum/trending.php)

If you go to anything else (say Airlines & Mileage programs, and then use THAT menu section, you can get to the main forums)