Forum title render array structure has changed, now uses a theme hook/template

When you visit the /forum/x page, related forum titles with markup are available in table format.

Before

Earlier this title was coming from .module file in markup like this.

$row[] = [
          'data' => [
            $topic->icon,
            [
              '#markup' => '<div class="forum__title"><div>' . $topic->title_link . '</div><div>' . $topic->submitted . '</div></div>',
            ],
          ],
          'class' => ['forum__topic'],
        ];

After

Now this render array has changed and the markup has been removed in favor of a theme hook/template. The new template forum-topic.html.twig template has been added to the module and the stable9 theme.

Themers that wish to customize the forum title should override the template forum-topic.html.twig by copying it to their theme's template folder and editing as appropriate.