Drupal 8+ reset module configuration to install defaults programmatically

Should you run into the situation where you need to reset the module config to the installation state (for what ever reasons), then this snippet might help you:

\Drupal::service('config.installer')->installDefaultConfig('module', $module);

For example in an update hook:

/**
 * Implements hook_update_N().
 */
function HOOK_update_10001(&$sandbox) {
  $module = basename(__FILE__, '.install');
  \Drupal::service('config.installer')->installDefaultConfig('module', $module);
  return t('Module @module config was reset to installation defaults. You may want to check the settings page.', ['@module', $module]);
}