After downloading and installing the new Dune content today, when I tried to select the Dune Activities pane from the sim main menu/landing page, I was taken to the Marketplace page which showed that the content is installed. I was not actually taken to any activities at all. Conversely, selecting the Maverick activities correctly took me to the specific Maverick-related activities included with that expansion.
After quitting the sim entirely and reloading, the Dune-related activities were properly displayed.
Posting this to see if my experience is unique, and possibly suggest this to anyone else that experiences it.