Tripoli: Footer organisation

Hi all – can anyone figure out how to split the secondary navigation bar in the footer of the Tripoli theme into multiple columns with headings? I’ve tried a few methods, but there doesn’t seem to be an easy way to organise them.

My code:

<footer class='c-footer'>
  <div class='o-grid c-footer__content'>

    {{> social-icons }}

  <a href="#/portal/signin" class="c-btn c-btn--small">Sign In</a>

    {{#if @site.secondary_navigation}}
      <ul class='u-plain-list c-footer-nav'>
        {{ navigation type='secondary' }}

<div class='c-footer__logo'>
  <img class='c-footer__logo' src='IMAGE LINK' alt='Partnerships'>

<div class='c-footer-copy'>
  Copyright &copy; {{ date format='YYYY' }} {{ @site.title }}. 
  <p>All articles are licensed under <a href="">CC BY-NC-ND 4.0</a>.</p>
  <p>Media belongs to respective owners.</p>