In order to authenticate with ArgoCD, we recommend using an AWS IAM Identity Center SAML Application. These apps can use existing Identity Center groups that we've already setup as part of the Identity layer.
The deployment process for ArgoCD includes setting up access tokens for a number of responsibilities. We will need to create the desire state repositories with necessary access, create Webhooks for these repos, grant the app in the EKS cluster permission to send notifications, and grant access for GitHub workflows.
Setup Synchronous Notifications for Argo CD with GitHub Commit Statuses
Learn how to use vanity domains with EKS
These are some additional tutorials that will help you along with the associated EKS components.