Hey Glen, I’m doing some personal project work in this area. There’s no CSV, etc. but the user details ( everything but access-groups ) can be retrieved through the API.
If you’re trying to maintain a synchronized subscriber list in ConvertKit, you’ll need to use the webhooks and automation to keep convertkit’s list current. There are a few issues with the Membership API currently however that will make this tricky at the moment.
Details in this post in the Memberships BETA forum if you’ve joined.