Set up your Synology NAS as an LDAP server to provide account authentication services. The Provider-Consumer architecture is an ideal solution if you have multiple clients located in different physical areas.
LDAP, or Lightweight Directory Access Protocol, is a directory service that can be installed on a Synology NAS. It is aimed at systems running Unix, Linux, and macOS. For a network with Windows servers and clients, I prefer Windows Active Directory or Syn