Enable plugin for all users

Thanks, @mingsong. Although my question would be for current users as well, enforcing the plugin in stead of having users do this themselves. A one-of SQL-update statement could be enough for me, I'll look into that.

Just for the record. I have used the following:

/**
 * Voeg tfa_email_otp toe aan het plugin-segment voor alle actieve gebruikers.
 */
function mymodule_update_11003(&$sandbox) {
  $user_data = \Drupal::service('user.data');
  $time = \Drupal::time()->getRequestTime();

  if (!isset($sandbox['uids'])) {
    $sandbox['uids'] = array_values(
      \Drupal::entityQuery('user')
        ->accessCheck(FALSE)
        ->condition('status', 1)
        ->execute()
    );
    $sandbox['total'] = count($sandbox['uids']);
    $sandbox['current'] = 0;
  }

  $batch_size = 50;
  $slice = array_slice($sandbox['uids'], $sandbox['current'], $batch_size);

  foreach ($slice as $uid) {
    $settings = $user_data->get('tfa', $uid, 'tfa_user_settings');

    if (!is_array($settings)) {
      $settings = [];
    }

    if (!isset($settings['data']) || !is_array($settings['data'])) {
      $settings['data'] = [];
    }

    if (!isset($settings['data']['plugins']) || !is_array($settings['data']['plugins'])) {
      $settings['data']['plugins'] = [];
    }

    $settings['data']['plugins']['tfa_email_otp'] = 'tfa_email_otp';

    if (!isset($settings['status'])) {
      $settings['status'] = 1;
    }

    $settings['saved'] = $time;

    if (!isset($settings['validation_skipped'])) {
      $settings['validation_skipped'] = 0;
    }

    $user_data->set('tfa', $uid, 'tfa_user_settings', $settings);
    $sandbox['current']++;
  }

  $sandbox['#finished'] = $sandbox['total'] > 0
    ? ($sandbox['current'] / $sandbox['total'])
    : 1;

  return t('TFA Email OTP is toegevoegd aan data.plugins voor @current van @total actieve gebruikers.', [
    '@current' => $sandbox['current'],
    '@total' => $sandbox['total'],
  ]);
}