I was facing the same situation in my instance, the issue being the category icons theme component, as it replaces the default renderer with the custom one that shows the icon beside the category name.
I’ve just submitted a pull request that fixes it by mirroring the default renderer’s way of showing the topic count and I installed my fork of the theme component https://github.com/renato/discourse-category-icons in my instance to restore the default behavior while/if the pull request isn’t accepted.