Add AWS EC2 instance to existing Availability Group I currently have an AG with 2 replicas both running SQL Server 2016. These are both located on premise. I was looking to add a third node using a AWS EC2 instance and asynchronous replication.

Networking issues aside, is this an acceptable approach? 

The only resources I can find on the internet appear to use distributed AGs but that would mean having a second EC2 instance in AWS
I assume it would be like this hybrid it: disaster recovery scenario but with AWS instead of Azure. There is an interesting point in the article about having your Active Directory available in the cloud. 

I think you'd have to give some thought to how quorum would work. For example, what would happen if you did a manual failover to the cloud instance, then later your on-premises instances came back online? 

HTH