RankMath SEO: FAQ block with collapsible headers aka an accordion, see full blog post: https://silvanhagen.com/writing/rankmath-faq-block-accordion/

rankmath-faq-accordion-all-items-closed.js

//
// This version hides all answers by default.
//
(function ($) {

    var rankMath = {
        accordion: function () {
            $('.rank-math-block').find('.rank-math-answer').hide(); // hides all answers by default
            $('.rank-math-block').find('.rank-math-question').click(function () {  
                //Expand or collapse this panel
                $(this).nextAll('.rank-math-answer').eq(0).slideToggle('fast', function () {
                    if ($(this).hasClass('collapse')) {
                        $(this).removeClass('collapse');
                    }
                    else {
                        $(this).addClass('collapse');
                    }
                });
                //Hide the other panels
                $(".rank-math-answer").not($(this).nextAll('.rank-math-answer').eq(0)).slideUp('fast');
            });

            $('.rank-math-block .rank-math-question').click(function () {
                $('.rank-math-block .rank-math-question').not($(this)).removeClass('collapse');
                if ($(this).hasClass('collapse')) {
                    $(this).removeClass('collapse');
                }
                else {
                    $(this).addClass('collapse');
                }
            });
        }
    };

    rankMath.accordion();

})(jQuery);

rankmath-faq-accordion-first-item-open.js

//
// This version shows the first answer by default.
//
(function ($) {
  var rankMath = {
    accordion: function () {
      $(".rank-math-block").find(".rank-math-answer:not(:first)").hide(); // shows the first answer by default
      $(".rank-math-block .rank-math-question:first").addClass("collapse"); // adds the proper class for the toggle
      $(".rank-math-block")
        .find(".rank-math-question")
        .click(function () {
          //Expand or collapse this panel
          $(this)
            .nextAll(".rank-math-answer")
            .eq(0)
            .slideToggle("fast", function () {
              if ($(this).hasClass("collapse")) {
                $(this).removeClass("collapse");
              } else {
                $(this).addClass("collapse");
              }
            });
          //Hide the other panels
          $(".rank-math-answer")
            .not($(this).nextAll(".rank-math-answer").eq(0))
            .slideUp("fast");
        });

      $(".rank-math-block .rank-math-question").click(function () {
        $(".rank-math-block .rank-math-question")
          .not($(this))
          .removeClass("collapse");
        if ($(this).hasClass("collapse")) {
          $(this).removeClass("collapse");
        } else {
          $(this).addClass("collapse");
        }
      });
    }
  };

  rankMath.accordion();
})(jQuery);

rankmath-faq-accordion.css

#rank-math-faq .rank-math-list-item {
    margin-bottom: 1em;
    margin-top: 1em;
    border-bottom: 1px solid #fff;
}

.rank-math-question {
    cursor: pointer;
    position: relative;
    display: block;
    padding-right: 1em;
    margin-right: 1em;
    font-weight: 300;
    margin-top: 30px;
}

.rank-math-question:after {
    position: absolute;
    right: 5px;
    top: 0;
    content: "\2715";
    transform: rotate(-45deg);
    transition: all 150ms ease-in-out;
}

.rank-math-question.collapse:after {
    transform: rotate(0deg);
}

.rank-math-question:hover {
    opacity: 0.8;
}