Theming link fields, getting URL value
Ok... found my answer. 

There are two ways you could do this. One way, is in the themename.theme file:

function mytheme_preprocess_field(&amp;$variables) {
  if ($variables['element']['#bundle'] == 'motivation_card' &amp;&amp; $variables['element']['#field_name'] == 'field_link') {
    foreach ($variables['items'] as $index =&gt; $item) {
      $variables['items'][$index]['content']['url'] = $item['content']['#url']-&gt;toString();
    }
  }
}


Another (preferable) way that I used is to use the render_var twig function.

{{ render_var(item.content['#url']) }}