I've made a fork and a merge request (!75) thanks to the patch in comment #24 ✨ Add an option to send HTML format opt-in / subscribe mails Postponed . Tested on version 4.0.0 and also with the Drupal Symfony Mailer → module. This patch solved the problem.
sergio.rizo → changed the visibility of the branch 4.x-3003811 to hidden.
I was wrong, this issue has already been reported https://www.drupal.org/project/simplenews/issues/3003811 ✨ Add an option to send HTML format opt-in / subscribe mails Postponed
I was wrong, this issue has already been reported https://www.drupal.org/project/simplenews/issues/3003811 ✨ Add an option to send HTML format opt-in / subscribe mails Postponed
I was wrong, this issue has already been reported https://www.drupal.org/project/simplenews/issues/3003811 ✨ Add an option to send HTML format opt-in / subscribe mails Postponed
sergio.rizo → made their first commit to this issue’s fork.
sergio.rizo → created an issue.