I am trying to use
hook_form_alter() to change the details of the CiviCRM Payment Processor for specific users (to change from live mode to test mode).
On Drupal 7 it's in
$form['submitted'] when Page 2 is rendered. Many items are already there on Page 1, but this is not.
Are these somewhere else, or do I have to use a different mechanism, in Drupal 9?