I'd like to have a listener understanding HTTP/2 without TLS ("prior knowledge HTTP/2"). The listener should then translate the received traffic into HTTP/1.1 and forward it to a desired location.
What would be an easy way to achieve this?
HAProxy appears to be a natural first choice, but unfortunately, non-TLS/ALPN listeners aren't currently supported
As for Apache, this appears relevant and appears to imply it's not possible (not sure, as I have little experience with Apache):
mod_proxy_http2 supports HTTP/2 only, it does not provide any downgrades to HTTP/1.1. This means that the backend needs to support HTTP/2 because HTTP/1.1 will not be used instead.
If there's a way to do this with Apache or Nginx, a pointer to a sample configuration file I could start from would be helpful.
This is for penetration testing purposes.