I set up a custom Subscription Form being sent to “/wp-json/newsletter/v2/subscriptions” a while ago and eventually got everyhting to work.
RIght now I am experiencing one issue with my listsobject as it is being ignored when creating the new subscriber.
I am using this syntax (as the example in the Swagger UI):
Hi, which version of the Newsletter API are you using? Could you kindly check the addon version? There was a bug on the previous version.
The second format (array) can be used with a negative number to unset a list (yes, it is not correctly documented).