How's the IPv6 support?

Namikoda supports IPv6 natively, both as a first-class component of our data as well as in our infrastructure. All of Namikoda's web endpoints are reachable over IPv6. See the IPv6s field for more about that part of the IpsFor object.

Should I use IP whitelisting to replace authenticated connections?

No. IP whitelisting is a good part of a defense-in-depth strategy that can be added to more sophisticated authentication strategies. It should not be considered a replacement.