No, they haven’t.
Many, many spooks and bureaucrats who had direct or indirect knowledge of the coverup have said that they were told it was the USSR. This was exactly how the plan was supposed to go.
The dozen or so people responsible for the actual coup are long dead and their great grandchildren still go to private schools and belong to country clubs.
For example...
https://nypost.com/2021/02/22/soviets-ordered-lee-harvey-oswald-to-kill-jfk-ex-cia-chief/