Passing a URL variable to category.php

While I see this has been discussed over and over .. none of the solutions seem to work for my case:

I need to pass a url variable to my category.php file. Currently my category page is at https://www.ads-software.com/category-slug/ I am using the SEO plugin to rewrite https://www.ads-software.com/category/category-slug and remove the /category/ part. Also, the settings formy permalinks are set to this option in the settings menu: ‘https://www.ads-software.com/sample-post/’

Now I need to be able to pass a variable in the URL like:

https://www.ads-software.com/category-slug/?type=VALUE or https://www.ads-software.com/category-slug/VALUE

where “type” is the name of the variable and VALUE is its value

I have tried using this piece of code in my functions.php file:

<?php
   add_filter('query_vars', 'parameter_queryvars' );
   function parameter_queryvars( $qvars )
     {
        $qvars[] = 'type';
        return $qvars;
     }
    global $wp_query;
     if (isset($wp_query->query_vars['type']))
      {
        print $wp_query->query_vars['type'];
      }
?>

However, when I try to open https://www.ads-software.com/category-slug/?type=something or https://www.ads-software.com/category-slug/something I get “nothing found” and “Page not found” pages.

How do I properly pass a variable to a category page?