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Note: Private endpoint is available in HDInsight clusters deployed in a virtual network.
You need to deploy the cluster in a VNet you can access it using the private endpoint https://CLUSTERNAME-int.azurehdinsight.net. This endpoint resolves to a private IP inside the VNet for cluster access.
For more details, refer “Azure HDInsight virtual network architecture” and “Secure incoming traffic to HDInsight clusters in a virtual network with private endpoint”.
Hope this helps.