Constant Contact Module (or other email integrations)

A long time ago, there was a constant contact integration module with Drupal 7. It seems that it no longer works, so porting it would not be helpful.

https://www.drupal.org/project/constant_contact/issues/3305871

Is anyone using Constant Contact and Backdrop CMS with anything more than an embedded email list sign up form?

Should there be a Constant Contact integration with Backdrop CMS, or is that use case not common enough anymore?

Anyone have any idea how difficult it would be to create a module like this? I expect it all depends upon the Constant Contact API.

There is a Mailchimp module for Backdrop CMS. But, it seems to lack a maintainer and only has two installations.