I literally don’t believe this. I do believe that you won’t read about them on the open internet though. The human condition is universal, and includes humor. It’s dangerous to “other” the entire population of a country.
Also, as you point out, Ivan Standupkov doesn’t even have to be particularly good because the material that surrounds him practically writes itself.
There are plenty, and they aren't exactly hiding either. All they need to make sure is avoid overly political jokes. You haven't heard of them because their content is entirely in Russian.