With WP 6, the theme does not show comments anymore

I have a, currenrly archived, blog I created using the Adventure Journal theme in 2013. The blog is no longer active, but I want to keep it available as an archival source.

When the blog was active, users could post comments to the articles. However, with the current WordPress version I use (version 6.0.2), I noticed that the comments themselves are no longer displayed. Under each article, it is indicated how many comments are given to the article, but the list remains empty.

What I did see in the generated HTML is the following:

<div id="comments">
 <h3 id="comments-title">6 Responses to <em>De eerste zes weken thuis</em></h3>
 <ol class="commentlist">
 <!-- #comment-## -->
 <!-- #comment-## -->
 <!-- #comment-## -->
 <!-- #comment-## -->
 <!-- #comment-## -->
 <!-- #comment-## -->
 </ol>
 </div>

To me this indicates, that the comments themselves are somehow seen, but the actual comments cannot be shown (there are 6 comments in this example, and there are also 6 HTML-comments in the ordered list).

Any idea how to fix this (on my own machine)?