Redirect traffic: LAN client > OPNsense > HAProxy > server

[Vaseer]

I am not sure if what I have imagined is possible or not, so I am here to ask for your help 

I have unRAD server with 2 separate dockers - Nextcloud and Collabora - and I would like to achieve, that connection from Nextcloud to Collabora would go through HAProxy (using Let's Encrypt cert) - HAProxy is installed on OPNsense.
Is it possible to assign local IP (10.0.0.X) to HAProxy (second local IP for OPNsense, that is forwarded to HAProxy?) so I can point Nextcloud to local IP of HAProxy which is using Let's Encrypt cert for https. HAProxy would then connect to Collabora.

Thank in advance.