Thanks Alvaro for your response, have answered your questions below
Q: you set this at build time and then each VM deployed from this will inherit?
A: No, that is not the case, we will perform regression to validate the application during image backing process this shall bypass the virtual network hub by enabling Accelerated Networking to the azure endpoints.
Q: or this is something you can enable at run time? ie on a new VM from the packer template.
A: No, accelerated Network cannot be enabled in runtime.
Q: Seems you are using packer as a sort of CI for Infra?
A: Yes, we use packer for CI.