get_node_aliases

function getNodeAliases($langcode = 'en') {
    $aliases = [];
    $nids = \Drupal::entityQuery('node')
            ->condition('status', 1) // published
            ->condition('langcode', $langcode)
            ->execute();
    foreach ($nids as $nid) {
        $system_path = '/node/' . $nid;
        $path_alias = db_query("SELECT alias FROM {url_alias} WHERE source = '$system_path' AND langcode = '{$langcode}'")->fetchField();
            $aliases[] = $path_alias;
    }
    return $aliases;
}