Version 8.5.2 of DG Operator allow to enable RESP and Memcached protocol.
But there is no chapter which explain how it can be achieved.

It is expected to have that within the Operator documentation.
The endpoint configuration should be included.

 
apiVersion: v1
kind: ConfigMap
metadata:
  name: infinispan-configuration-custom
  namespace: ptc-sisu
data:
  infinispan-config.xml: |
    <infinispan
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="urn:infinispan:config:15.0 http://www.infinispan.org/schemas/infinispan-config-15.0.xsd              urn:infinispan:server:15.0 http://www.infinispan.org/schemas/infinispan-server-15.0.xsd"    xmlns="urn:infinispan:config:15.0"    xmlns:server="urn:infinispan:server:15.0">
      <server xmlns="urn:infinispan:server:15.0">
          <endpoints>
            <endpoint socket-binding="default" security-realm="default">
              <memcached-connector />
              <rest-connector />
              <resp-connector />
            </endpoint>
          </endpoints>
        </server>
    </infinispan>