All discussion category pages have the same canonical url (/page/discussions-category). If we go to this page, we will see an empty discussion block similar to the page (/page/discussions-home). There is also another category page (/page/discussions-categories).
Hello @Ivan Mishchenko !
The first mentioned page (/page/discussions-category) requires a GET argument to show the discussion list by this category. The second page is the old page with the block of categories, now it exists on the discussions home page too.
It just turns out that all category pages with GET parameters link to the same page. For users, this does not matter, but for search bots, it is confusing, since the structure of all pages that are related to discussions is disrupted.