We have installed only consul agents on k8 cluster using the helm charts.

https://www.consul.io/docs/platform/k8s/helm.html

We have a separate consul server installed on a cluster (this is non-k8 cluster) outside my k8 cluster.

Is it possible to join my agents to the consul server cluster (non-k8 cluster)?

I have checked the below link

https://www.consul.io/docs/agent/cloud-auto-join.html#tag_value-1

However, this describes only about joining the consul agent joining to the existing k8 consul server.

consul agent -retry-join "provider=k8s label_selector=\"app=consul,component=server\""