try to install the wpusers integration (free on extensions panel) and set the list when ther user is registered. If the custom form and custom registration are well written it should work.
If you want to add the lists in the subscription form, things are more complex.
This is what I’m looking to do as well. I want the user to select multiple lists (backed by automated channels) during registration. I’m using a plugin to handle registration forms (Ultimate Member) which I believe should be compatible. Do I just have to add custom checkboxes to the registration form? Something else?