Drupal - Change a normal submit 'input' type to 'button' type with button tag

Well that was quick... I used my intuition and was able to accomplish it by doing the following:

In mytheme.theme:

/**
 * @param $suggestions
 * @param array $variables
 */
function mytheme_theme_suggestions_input_alter(&$suggestions, array $variables) {
  $element = $variables['element'];

  if (isset($element['#attributes']['data-twig-suggestion'])) {
    $suggestions[] = 'input__' . $element['#type'] . '__' . $element['#attributes']['data-twig-suggestion'];
  }
}

/**
 * @param $form
 * @param \Drupal\Core\Form\FormStateInterface $form_state
 * @param $form_id
 */
function mytheme_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  if ($form['#id'] == 'views-exposed-form-search-results') {  
    $form['actions']['submit']['#attributes']['data-twig-suggestion'] = 'search_results_submit';
    $form['actions']['submit']['#attributes']['class'][] = 'search-box__button';
  }
}

In input--submit--search-results-submit.html.twig

{#
/**
 * @file
 * Theme override for an 'input' #type form element.
 *
 * Available variables:
 * - attributes: A list of HTML attributes for the input element.
 * - children: Optional additional rendered elements.
 *
 * @see template_preprocess_input()
 */
#}
<button{{ attributes }}>
  <svg class="icon search-box__open">
    <use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/themes/custom/mytheme/build/img/svg-sprite.svg#icon-search"></use>
  </svg>
</button>

Form still submits and functions as expected. Is this the general approach or at least acceptable? I will go with this unless there is a better way.

You simply could use inline_template.

$build['hello']  = [
  '#type' => 'inline_template',
  '#template' => '<button type="button" class="search-box__button">
     <svg class="icon search-box__open">
       <use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/build/img/svg-sprite.svg#icon-search"></use>
     </svg>
   </button>',
];