Query on SQL Server 2017 Always-On

Hi All,

DC1: (servers are in WSFC)
DB_Server1
DB_Server2

DC2:
DB_Server3

DC1 and DC2 servers are located in different geo locations. Is it possible to configure SQL 2017 Always-On/SQL 2017 Distributed Always-On in above environmnet? 
As per my understanding, the servers should be in WSFC, but DC2 DB server is not in cluster, its standalone machine. If it's not possible to configure SQL always-On in above env, please suggest which SQL HA/DR solution i can use...