Sort shopify collection by last names

collection.liquid

<div class='collection-list no-pad rel'>
  <div class='outer'>
    <div class='container'>
      {% assign lnames = '' %}
      {% assign letters = '' %}
      {% for collection in collections %}
        {% if collection.title contains 'Designer:' %}
          {% assign name = collection.title | split: ':' | last %}
          {% assign rname = name | split: "" | reverse | join: "" %}
          {% assign lrname = rname | split: " " | first %}
          {% assign lname = lrname | split: "" | reverse | join: "" %}

          {% if lnames == '' %}
            {% assign lnames = lnames | append: lname | append: ':' | append: collection.handle %}
          {% else %}
            {% assign lnames = lnames | append: ',' | append: lname | append: ':' | append: collection.handle %}
          {% endif %}

          {% assign letter = lname | split: '' | first %}

          {% if letters == '' %}
            {% assign letters = letters | append: letter %}
          {% else %}
            {% assign letters = letters | append: ',' | append: letter %}
          {% endif %}
        {% endif %}
      {% endfor %}

      {% assign letters = letters | split: ',' | sort | uniq %}
      {% assign alpha = lnames | split: ',' | sort %}

      {% for letter in letters %}
        <h2 id='{{ letter }}' class='mb05 mt1 medium'>{{letter}}</h2>

        <div class='collection-list__cards f ais fw'>
          {% for value in alpha %}
            {% assign lname = value | split: ':' | first %}
            {% assign firstletter = lname | split: '' | first %}
            {% assign handle = value | split: ':' | last %}

            {% if firstletter == letter %}
              <div class='collection-list__card collection-list__card--designer'>
                {% include 'collection-card' with collection: collections[handle] %}
              </div>
            {% endif %}
          {% endfor %}
        </div>
      {% endfor %}
    </div>
  </div>
</div>