Need help with irule masking the url, please.

At the very least you should:

1. Rewrite the host header on incoming traffic (internal LTM) in case that's causing the server to send the redirect, and

2. Rewrite the Location header on outgoing redirects (internal LTM)

   when HTTP_REQUEST {
       HTTP::header replace Host "x.x.x.x:8020"
   }
   when HTTP_RESPONSE {
       if { [HTTP::header exists Location] } {
           HTTP::header replace Location [string map {"http://x.x.x.x:8020" "https://x.x.x.x"} [HTTP::header Location]]
       }
   }
   

That'll cover the incoming Host header to the web servers and outgoing redirects to the client. If that doesn't completely work, then there may still be internal document object references to deal with.