Enable classic editor without plugin

There is a popular plugin to disable the Gutenberg editor. Just a simple PHP code snippet, we can disable the Gutenberg editor for the site.

// Disable Gutenberg for all posts
add_filter('use_block_editor_for_post', '__return_false');

However, there is a simple way to enable the Gutenberg editor for specific post type (post/page/custom-post-type)

if ( is_admin() ):
    add_filter( 'use_block_editor_for_post', 'wpdocs_disable_block_for_post_type', 10, 2 );
endif;

function wpdocs_disable_block_for_post_type( $bool, $post ) {
    if ( 'post' === $post->post_type ):
        return false;
    endif;

    return $bool;
}