Configuring Availability group between Two SQL Server Failover Cluster Instances
You can try a &ldquo;distributed availability group&rdquo;:


  A distributed availability group is a special type of availability group that spans two separate availability groups. The availability groups that participate in a distributed availability group do not need to be in the same location. They can be physical, virtual, on-premises, in the public cloud, or anywhere that supports an availability group deployment. This includes cross-domain and even cross-platform - such as between an availability group hosted on Linux and one hosted on Windows. As long as two availability groups can communicate, you can configure a distributed availability group with them.