How do I list custom taxonomy terms with the links?

by

WebElain was correct but, you’ve also got the HTML escaped. The entire chunk of code should be:

  function thb_display_category_cus() {
  if ('portfolio' === get_post_type() ) {
    $categories = get_the_term_list( get_the_ID(), 'portfolio-category', '', ', ', '' );



 echo $categories


      } else {
        the_category(', ' );
      }
    }