120.disable the block editor only for particular post types

 add_filter('use_block_editor_for_post_type', 'prefix_disable_gutenberg', 10, 2);

function prefix_disable_gutenberg($current_status, $post_type)

{

    // Use your post type key instead of 'product'

    if ($post_type === 'cities') return false;

    return $current_status;

}