https://www.tvmaze.com/search?q=Expedition+Unknown
was gonna update the latest version of this, but when I visited official site, the episode is listed as season 6.
Found an article referring to it as a special event: https://www.hollywoodreporter.com/live-feed/discovery-channel-sets-special-expedition-unknown-1147116
and the host's page : http://www.joshuagates.com/
just want to be clear if we consider this a separate show or is it a continuation or specials of main series?
Looks like you know more about this franchise than most.
I don't think you'd class it as specials of the main series as they all appear to be in a relatively serialised format, which doesn't match our definition of a special.
According to the Data Policies, press releases take more priority over websites (which are often displayed a different way for convenience or due to technical limitations).
To me, it seems like this is a themed version of the main show.
