I do not think Virtual Appliance can be deployed as a command line interface Linux setup even though it uses Docker internally.
From my understanding the Identity Security Cloud Virtual Appliance is provided as a packaged virtual machine image, like OVA for VMware or VHD, for Azure not something you install manually from scratch.
Inside the Virtual Appliance:
It runs a Linux operating system
It includes Docker containers
It comes with SailPoint managed services and configurations
Even though Docker is part of Virtual Appliance setup:
SailPoint does not provide Docker images for independent deployment
The Identity Security Cloud Virtual Appliance depends on orchestration, certificates and a secure bootstrap process
There are built-in security hardening measures and trust configurations tied to the Identity Security Cloud Virtual Appliance image
Registration with the Identity Security Cloud relies on preinstalled agents and configuration scripts
overall Virtual Appliance is not really designed to be deployed as a plain command line interface based Linux environment it is meant to be used as a fully managed prebuilt Virtual Appliance. If anyone has better idea/suggestions feel free to add.