Some entries are missing in vyos-build/data/architectures/arm64.toml for builds for the arm64 architecture.

The current files are as follows:

# Packages included in ARM64 images by default
packages = ["grub-efi-arm"]
bootloaders = "grub-efi"

The correct grub-efi package name for ARM64 is grub-efi-arm64.

In addition, It is also assumed that additional packages, repositories and kernel flavor are needed for arm64.toml as well as those contained in vyos-build/data/architectures/amd64.toml.

Thus, the correct file contents would be as follows:

additional_repositories = [
  "deb [arch=arm64] https://repo.saltproject.io/py3/debian/11/arm64/3004 bullseye main",
  "deb [arch=arm64] http://repo.powerdns.com/debian bullseye-rec-48 main"
]

kernel_flavor = "v8-arm64-vyos"

# Packages included in ARM64 images by default
packages = [
  "vyos-linux-firmware",
  "telegraf",
  "grub-efi-arm64"
]
bootloaders = "grub-efi"

Perhaps you intentionally did not include an entry in relation to "Determine the list of flavors we do intend to support." as stated in https://phabricator.vyos.net/T3664 ?

If so, it may be legitimate to define them as flavors such as iso-arm64.