I believe subtle audio changes were made to the other two films in 1993 but don’t quote me on that. Nothing visual as far as I know was changed with the last two films.
As far as I can tell: Aside from one missig sound effect in Empire, no. Unless you take into account the teathrical mono mix for Empire which had some different content but with Jedi at least I don’t think there were any changes done before 97.