How to set ingressClass on IngressRoute CRD?

I'm deploying separate internal and external ingress controllers. I have set isDefaultClass: false on the second, and given it a unique ingresClass name in providers: kubernetesCRD: ingressClass:

My question is how to specify this ingressClass in my IngressRoute resources? The docs mention using the "" annotation here: Kubernetes IngressRoute & Traefik CRD - Traefik

however this annotation is considered deprecated: Ingress | Kubernetes

Is this still the best way to specify an ingressClass?