Landing page with faded background


I’m trying to achieve something similar like Nomad Forum does, where

  • Individual threads can still be viewed when accessed directly via the URL (e.g. linked on another site) or via Google Search Results
  • When going to the root page it shows a LOGIN and JOIN button with the background visible, but faded (see screenshot below)
  • JOIN redirects to an off-discourse landing page

I just signed-up for the paid hosted solution. The changed I’d like to do are they even possible or would I need to use a self-hosted solution and fiddle with the code?