Anthos ona AWS in now GA an Anthos on Azure is in a preview. GKE on AWS is a simplified installation of the Admin control plane. It uses AWS Elastic Compute Cloud (EC2), Elastic Block Storage (EBS), and Elastic Load Balancer (ELB) services. The bellow diagrams shows high level architecture. The deployment is done using Terraforms.
The details about architecture you can found here: https://cloud.google.com/anthos/gke/docs/aws/concepts/architecture
The installation process can be found her: https://cloud.google.com/anthos/gke/docs/aws/how-to/prerequisites
Note: the docs are still pending update as it shows „Beta”
The war between Anthos and VMware Tanzu is getting more exciting to watch :).