Azure
Implemented in Azure. See Azure Load Balancer.
Google Cloud
Google Cloud implements this in external and internal passthrough Network Load Balancers. https://cloud.google.com/load-balancing/docs/network
AWS
AWS NLB does not make use of it.
https://repost.aws/questions/QUNtYRmHbDRNyJ1g8ltLwnOA/nlb-ip-preservation-over-peering-target-group
There is no DSR as you correctly mentioned, the AWS SDN handles the connection in such a way that the Client IP is preserved and traffic is still (symmetrically) routed via NLB.