Gutentor works with any theme of WordPress repository regardless of coding standards of theme with WordPress 5.0 or later. The latest version of WordPress is always recommended. The Gutentor Pro plugin is dependent on Gutentor free plugin which means it is mandatory to install and activate Gutentor free plugin to work with the Gutentor Pro plugin.
Note: Gutentor Pro doesn’t work itself only in WordPress. It needs Gutentor Plugin.