Is there a way actually to extract certificates from the games buyed and downloaded form the eshop?

No because they are unique to not only to the Switch console that they are installed onto but also to the game as well. See here for more information: https://www.reddit.com/r/SwitchHacks/comments/8rxg26/psa_strong_antipiracy_measures_implemented_by/Is there a way actually to extract certificates from the games buyed and downloaded form the eshop?
