function is_gutenberg_page() {
            if ( function_exists( 'is_gutenberg_page' ) &&
                 is_gutenberg_page()
            ) {
                // The Gutenberg plugin is on.
                return true;
            }

            $current_screen = get_current_screen();

            if ( method_exists( $current_screen, 'is_block_editor' ) &&
                 $current_screen->is_block_editor()
            ) {
                // Gutenberg page on 5+.
                return true;
            }

            return false;
        }