How to add "#" as a menu link?

Question

How can I simply add "#" as a menu link in Drupal 8? I want to have:

<a href="#" ... output as a menu link.

Do I have to define my own route token akin to <nolink> and write a custom LinkGenerator class to handle that case?

i.e.:

elseif ($url->isRouted() && $url->getRouteName() === '<nolink>') {
      $generated_link = new GeneratedNoLink();
      unset($attributes['href']);
    }
elseif ($url->isRouted() && $url->getRouteName() === '<hashonly>') {
      $generated_link = new GeneratedLink();
      $attributes['href']= "#";
    }

Or is there an easier place to do this without disrupting the render pipeline?