HTTP2 to HAProxy and HTTP3 to backend servers

I am not sure this question been asked before, and searched forum without result and googled no answer, so ask here.

I want to resolve 1M HTTP2 connections issue, that limit one machine can only have 65000 TCP connections outbound.

The configuration will be:
1M HTTP2 connections to HAProxy, and HAProxy using HTTP3 to backend servers, using hash to do session stickiness.

Anybody experiment this? Or this is the standard operation on HAProxy? Any solution by using HAProxy? thanks