Drupal 9 entity.repository load entity by UUID
use SymfonyComponentHttpKernelExceptionHttpException;
$node_uuid = 'UUID STRING HERE';
try {
$node = Drupal::service('entity.repository')->loadEntityByUuid('node', $node_uuid);
$nid = $node->id();
unset($node);
} catch (Exception $e) {
throw new HttpException(400, 'Node UUID does not match one in the system.');
}