add_filter( 'generate_post_date_output', 'tu_add_cats_to_date' );
function tu_add_cats_to_date( $output ) {
$categories_list = get_the_category_list( _x( ', ', 'Used between list items, there is a space after the comma.', 'generatepress' ) );
if ( $categories_list ) {
return $output . ' | ' . $categories_list;
}
return $output;
}