E-mail not send when opt_in_status is set but empty

Meanwhile, we end-users can add the following lines to the form under Build » Source:

opt_in_status:
  '#type': value
  '#title': opt_in_status
  '#value': 'Double opt-in confirmation mail pending'

Also, I figured out that of the 2 handlers this module provides, only the DoubleOptInEmailWebformHandler is useful. The “Compatible“ handler doesn’t yet understand the [email-confirmer:confirmation-url] token as far as I can tell. In fact, it looks like the “Compatible“ handler is just an old copy of the one that is shipped with the vanilla webform module.

And in short, I got the module to work and am happy.