Request for Information on Traffic-management for the services not receiving any traffic through the Ingress Gateway

Hi all,

I am relatively new to Istio, and would like to post the following request for the specific information.
The traffic routing for the requests travelling through the ingress gateway could be done with the VirtualService,DestinationRule and EnvoyFilter API components.
We have the cluster with additional (infrastructure) components on the Kubernetes Cluster like Prometheus and the AlertManager and others. We thought about enabling the Sidecar Injection(for mTLS) also for them, and have a few questions to it.
The traffic between those components is not going through the Gateway, and I know so my guess would be to use the EnvoyFilters for defining the rules in the Sidecars for allowing that communication.
But if possible would like to make a request for further information on such communication between different services/components.

Thanks in advance!