Can we access Stacker data via an API other than Zapier? I’m running into an issue where Zapier can’t respond with any data when calling a webhook, and thus cannot be used in my case. I need to use a different system, but AFAIK only Zapier has a Stacker API integration, and the Stacker API is private so I can’t build a custom workaround using code.

This is true for Classic. Astra does have an Open API.