Help using Spegel & Talos & Autoscaler & Hetzner Cloud image build

[hoobiboobi]

Hi! I'm trying to integrate Spegel into a Kubernetes cluster running on Talos with the Talos autoscaler in Hetzner Cloud. However, I'm facing challenges due to the way node configuration is handled in autoscaled environments.

The Spegel Talos integration guide suggests patching the nodes after they are created, but that approach doesn't work well for me because nodes are created dynamically by the autoscaler. Instead, I want to embed the required Spegel configuration into the Talos image during the build process.

Here’s my current setup:

I use the siderolabs/talos Terraform provider to generate a Talos image using Talos Image Factory.
Then I push the image to Hetzner Cloud using Packer (with schematic_id and talos_image_url).
I use these prebuilt images to launch my autoscaled Kubernetes nodes.
The problem:

I’ve tried embedding Spegel configuration (e.g. root/etc/cri/conf.d/20-customization.part or enabling the registry mirror setup) during the Talos Image Factory stage.
However, it looks like not all parameters are applied — the resulting schematic_id always stays the same unless I modify systemExtensions = { officialExtensions = [...] }.
When I try to include something custom in systemExtensions, the schematic ID doesn’t change and the image content doesn’t seem to reflect my changes.
What I tried:

 resource "talos_image_factory_schematic" "this" {
  schematic = yamlencode({
    customization = {
      systemExtensions = {
        officialExtensions = data.talos_image_factory_extensions_versions.this.extensions_info[*].name
      }
    },
    machine = {
      files = [
        {
          path    = "/etc/cri/conf.d/20-customization.part"
          op      = "create"
          content = <<-EOT
            [plugins."io.containerd.cri.v1.images"]
              discard_unpacked_layers = false
          EOT
        }
      ]
    }
  })
} 

My question:
What is the correct way to include custom Spegel-related configuration (like registry mirrors or containerd settings) into a Talos image that will be used by an autoscaler in Hetzner Cloud?

Any guidance or examples would be greatly appreciated!

Thanks in advance 🙏