Articles are text-only in any “Category” instead of HTML

The theme uses the_excerpt() instead of the_content().

I had created a child theme before (so I don’t modify the source theme directly: only the child one), so I only had to copy/paste the PHP file (archive.php) from source theme to child theme, and change the_excerpt() for the_content( __( 'Read more ›', 'my-domain' ) );