MYTHEME.theme snippet for language switcher block in Drupal 8+

mytheme.theme

<?php
// Changes the language switcher block to use country codes instead of long format country names
// So if the site was in English/Italian, the original switcher would show (at D9 iirc):
// English - Italian, and this code makes it into EN - IT (lack of correct formatting notwithstanding)
// This could easily be adapted to show flags etc instead I imagine.

/**
 * Implements hook_preprocess_block().
 */
function mytheme_preprocess_block(&$variables) {
  if ($variables['elements']['#id'] == 'languageswitcher') {
    $links = &$variables['content']['#links'];
    foreach ($links as $lang => $data) {
      $variables['content']['#links'][$lang]['title'] = $lang;
    }   
  }
}