Make block_content contextual links available in Layout Builder blocks.

drupal-block_content-contextual_links-layout.builder.php

<?php

function my_theme_preprocess_block(&$variables) {
  // Make block_content contextual links available in Layout Builder blocks.
  if(!empty($variables['content']['#block_content'])){
    if (empty($variables['title_suffix']) && isset($variables['elements']['content']['#contextual_links'])) {
      $variables['title_suffix']['contextual_links'] = [
        '#type' => 'contextual_links_placeholder',
        '#id' => _contextual_links_to_id($variables['elements']['content']['#contextual_links']),
      ];
    }
  }
}