Is there any possible a way to terminate HTTP/2 on AWS Application ELB, so that the web servers don't need to be configured to support HTTP/2?
Eles já não precisam ser.
No balanceador de carga de aplicativos (ELB / 2.0), é assim que funciona imediatamente. O ALB fala com as instâncias usando HTTP / 1.1 enquanto fala HTTP / 2 para o navegador, se o navegador suportar, caso contrário, HTTP / 1.x.
You can use HTTP/2 with HTTPS listeners. You can send up to 128 requests in parallel using one HTTP/2 connection. The load balancer converts these to individual HTTP/1.1 requests and distributes them across the healthy targets in the target group using the round robin routing algorithm. (emphasis added)
http://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-listeners.html