Distributed Always-On without Domain

Hi All,

We have requirement to configure Distributed Always-On from Data center1 to Data Center2 using SQL Server 2017 Ent edition.

DC1 (two nodes WSFC setup): SQLDB1, SQLDB2
DC2 (two nodes WSFC setup): SQLDB3, SQLDB4

The servers are in workgorup not in domain. Is it possible to configure Distributed SQL always-on from DC1 to DC2 without domain?

As per my understaning, using certificates it's possible to configure Distributed SQL always-on if all four nodes are in same cluster. Is this my understanding is correct?

Please guide me.