Palantir runs on the customer’s own cloud, or a major cloud provider of the customer’s choosing in the region of their choosing. There’s no data aggregation/sharing across customers, it works similar to AWS.

Source?

Edit: since someone already posted the guardian link i'll update mine with this one https://theconversation.com/palantir-privacy-fears-over-hand...

https://www.theguardian.com/society/2023/nov/21/patient-priv... very widely reported on - you'll find lots more reporting on Google.