GitHub keeps all the installation scripts in their Open Source repository https://github.com/actions/virtual-environments. They use packer to automatically create the virtual machine. This repository contians a seies of powershell scripts and instructions for running all of this in an Azure Virtual Machine but no where else.
This repository takes a fork of their packer scripts and converts them into a compatible *.pkr.hcl file. Then it uses the Hyper-V community builder tools to run the provisioning scripts on the Hyper-V virtual machine.