Renders a “fake” meta box with an information message,
shown on the block editor, when an incompatible meta box is found.

function do_block_editor_incompatible_meta_box( $data_object, $box ) {
	$plugin  = _get_plugin_from_callback( $box['old_callback'] );
	$plugins = get_plugins();
	echo '
';
	if ( $plugin ) {
		/* translators: %s: The name of the plugin that generated this meta box. */
		printf( __( 'This meta box, from the %s plugin, is not compatible with the block editor.' ), "{$plugin['Name']}" );
	} else {
		_e( 'This meta box is not compatible with the block editor.' );
	}
	echo '
';

	if ( empty( $plugins['classic-editor/classic-editor.php'] ) ) {
		if ( current_user_can( 'install_plugins' ) ) {
			$install_url = wp_nonce_url(
				self_admin_url( 'plugin-install.php?tab=favorites&user=wordpressdotorg&save=0' ),
				'save_wporg_username_' . get_current_user_id()
			);

			echo '
';
			/* translators: %s: A link to install the Classic Editor plugin. */
			printf( __( 'Please install the Classic Editor plugin to use this meta box.' ), esc_url( $install_url ) );
			echo '
';
		}
	} elseif ( is_plugin_inactive( 'classic-editor/classic-editor.php' ) ) {
		if ( current_user_can( 'activate_plugins' ) ) {
			$activate_url = wp_nonce_url(
				self_admin_url( 'plugins.php?action=activate&plugin=classic-editor/classic-editor.php' ),
				'activate-plugin_classic-editor/classic-editor.php'
			);

			echo '
';
			/* translators: %s: A link to activate the Classic Editor plugin. */
			printf( __( 'Please activate the Classic Editor plugin to use this meta box.' ), esc_url( $activate_url ) );
			echo '
';
		}
	} elseif ( $data_object instanceof WP_Post ) {
		$edit_url = add_query_arg(
			array(
				'classic-editor'         => '',
				'classic-editor__forget' => '',
			),
			get_edit_post_link( $data_object )
		);
		echo '
';
		/* translators: %s: A link to use the Classic Editor plugin. */
		printf( __( 'Please open the classic editor to use this meta box.' ), esc_url( $edit_url ) );
		echo '
';
	}
}