Azure AD Certification Based Authentication (CBA) is now in Public Preview. This is really exciting because this will allow customers to meet their PIV/CAC card multi-factor auth requirements without having to maintain ADFS servers for federated authentication.
Reference: https://techcommunity.microsoft.com/t5/azure-active-directory-identity/azure-ad-certificate-based-authentication-now-in-public-preview/ba-p/2464390