The VMware Horizon component that needs to be deployed to allow users to log into VMware Workspace ONE Access and connect to remote desktops and applications without having to provide Active Directory credentials is the Enrollment Server. The Enrollment Server is a standalone service that integrates with VMware Workspace ONE Access and enables True Single Sign-On (SSO) for Horizon clients that are using non-AD-based authentication methods such as RSA SecureID, RADIUS, or SAML1. The Enrollment Server requests short-lived certificates on behalf of the users from a certificate authority (CA), and these certificates are used for authentication to the Horizon environment2. The Enrollment Server must be installed and configured in the same domain or forest as the Connection Server, and it must have an enrollment agent certificate that authorizes it to act as an enrollment agent2.
The other options are not valid or feasible because:
A Replica Server is a Connection Server instance that replicates the Horizon LDAP configuration data from another Connection Server instance, and provides high availability and load balancing for user connections3. A Replica Server does not request or issue certificates for users, and it does not integrate with VMware Workspace ONE Access.
A Security Server is a Connection Server instance that resides within a DMZ and acts as a proxy for external user connections to the Horizon environment4. A Security Server does not request or issue certificates for users, and it does not integrate with VMware Workspace ONE Access. Security Servers are deprecated in Horizon 8 and replaced by Unified Access Gateways (UAGs)4.
A vCenter Server is a management platform that provides centralized control and visibility of vSphere hosts and virtual machines in the Horizon environment5. A vCenter Server does not request or issue certificates for users, and it does not integrate with VMware Workspace ONE Access.
References:
VMware Horizon 8.x Professional by Vmware1
Install and Set Up an Enrollment Server2
Install a Replica Connection Server Instance3
Install a Security Server4
vCenter Server Overview5