HTTP/2 is enabled per default for the load balancer, but for the target group!

According to this announcement and the AWS console the target groups do support HTTP/2 as well.

https://aws.amazon.com/blogs/aws/new-application-load-balancer-support-for-end-to-end-http-2-and-grpc/

However, the target groups are always configured to forward to connect via HTTP/1.1

This might have a performance impact