You are required to install Istio, but when running below command:
vcf package available get istio.kubernetes.vmware.com -n <packages_namespace>
the Istio package is not available/listed.
vSphere Kubernetes Service
The VKS Standard Packages repository is the required for obtaining the Istio package.
The above repository has not been added to you packages namespace.
You must first add the VKS Standard Packages repository using the below command:
vcf package repository add <vks-standard-repo-name> -url projects.packages.broadcom.com/vsphere/supervisor/packages/2025.8.19/vks-standard-packages:v2025.8.19 -n <packages_namespace>
-- where you replace <vks-standard-repo-name> with your required repository name and replace <packages_namespace> with your required packages namespace.
After adding the VKS Standard Packages repository you will then be able to run below command to get the Istio package.
More commands and details can be found here on setting up the VKS Standard Packages repository and details on installing Istio can also be found here.