javascript – Google Tag Manager trigger for content in shadow-root?

How do I create a UA trigger that fires when a user clicks on content in a #shadow-root inserted using JavaScript?

HTML is as follows, where the site I am working on is “site_A” and the site the inserted content is from is “site_B”:

<div class="site_A_class">
  <script src="site_B/script.js" ...></script>
</div>

In FF developer view, HTML appears as follows:

<div class="site_A_class">
  <script src="site_B/script.js" ...></script>
  <div>
    #shadow-root
    <div>
      <a class="click_me" href="site_B/url.html">...</a>
    </div>
  </div>
</div>

I want a trigger that fires when a user clicks on a.click_me. Things I have tried: (1) “click – just links” trigger with “click URL contains site_B”; (2) “click – all elements” with “click element matches CSS selector div.site_A_class”; (3) same, but matching “.site_A_class div div a”.; (4) “click – just links” trigger with “click class contains click_me”. Nothing fires.

Can it be done? If so, I’d appreciate pointers.