HAProxy SSL offloading, SSL backend, Let's Encrypt

[TravoltaX]

Hi there,

How to configure HAProxy for the following case:

1. Client (PC) connects via HTTPS (443) to HAProxy,
2. HAProxy offloading SSL to Let's Encrypt then,
3. Traffic is redirected to the port 443 server (server then uses its own local CA certificate for HTTPS response)

Other info:
Before I was using Windows Web Application Proxy. Communication between client and front-end server was via public ACME cert. Backend communication between WAP and application server was handled by local CA cert.
I would like to replicate similar setup using OPNSense, HAProxy, ACME.

Any help greatly appreciated!