FYI I’ve gotten around this by rewriting the HTML with JS on load, but it’s not ideal as updates to the topic won’t be reflected:
$(".category-list tr[data-category-id='5'] .category-description").html('Lorem Ipsum<ul><li>Bullet 1</li><li>Bullet 2</li></ul>');
I’ve also found another topic with the same question: https://meta.discourse.org/t/how-to-show-more-than-one-line-of-the-category-description-when-viewing-from-parent-category/133593