add_action('category_description', 'category_description_28072021', 90, 2);

function category_description_28072021($description, $term){

    if(is_admin()) return $description;

    //Get term data
    $term_id = isset($term->term_id) ? $term->term_id : $term;
    $category = get_term($term_id);
    $taxonomy = isset($category->taxonomy) ? $category->taxonomy : '';

    // term field data
    $post_count = get_term_field('count', $term_id);


    return  sprintf(__('Total post Count: %s. ', 'textdomain'), $post_count). $description;


}