exclude category

add_filter( 'jnews_default_query_args', function ( $args ) {
    $exclude = '8';
    if (! isset( $args['post__in'] ) ) {
        if ( isset( $args['category__not_in'] ) ) {
            $args['category__not_in'][] = $exclude;
        } else {
            $args['category__not_in'] = [$exclude];
        }
    }
    return $args;
}, 9999 );