here we go

[m1-debian] / installer_data.json

{
    "os_list": [
        {
            "name": "Debian bookworm (testing) packaged by Thomas Glanzmann",
            "default_os_name": "Debian",
            "boot_object": "m1n1.bin",
            "next_object": "m1n1/boot.bin",
            "package": "debian-base.zip",
            "supported_fw": ["12.3", "12.4"],
            "partitions": [
                {
                    "name": "EFI",
                    "type": "EFI",
                    "size": "512MB",
                    "format": "fat",
                    "copy_firmware": true,
                    "copy_installer_data": true,
                    "source": "esp"
                },
                {
                    "name": "Root",
                    "type": "Linux",
                    "size": "5GB",
                    "expand": true,
                    "image": "media"
                }
            ]
        }
    ]
}