[lucaspardue]

Do you mean forward proxies? The HTTP/3 draft currently specifies how the CONNECT method is used. At present, it only allows you to create an onward TCP connection. So you have a QUIC connection between client and proxy, and a TCP connection between proxy and server. Like so

        QUIC         TCP

client <----> proxy <----> server

Unfortuantely, this means that a HTTP/3 client has to tunnel HTTP/1.1 or HTTP/2 to the target server. I realised this was a shortcoming last year and prepared an I-D called HiNT that explores the problem space and some candidate solutions:

https://datatracker.ietf.org/doc/draft-pardue-httpbis-http-n...

This was presented, along with some nicer tunnel diagrams, at the IETF 102 meeting. Slides in pdf: https://github.com/httpwg/wg-materials/blob/gh-pages/ietf102...