You should check out Nixos. You make a config file that you can just copy over to as many machines as you want.

Sounds like you need nixos

that workflow seems fine if it works for you. seems overkill for debian but if it works i don't see anything wrong with it.

one way I do it is dpkg - l > package.txt to get a list of all install packages to feed into apt on the new machine then to setup two stow directories one for global configs. when a change is made and one for dot files in my home directory then commit and push to a personal git server.

Then when you want to setup a new system it's install minimal install then run apt install git stow

then clone your repos grab the package.txt run apt install < package.txt then run stow on each stow directory and you are back up and running after a reboot.

You could try using Hashicorp's Packer to generate images repeatably (usually more meant for cloud images though). Or NixOS (like others have mention), or Guix (like NixOS, but better in some ways, worse in others). You could make it an Ansible playbook, which would let you both make configured images, and just configure machines that already have an OS.

I do something similar with archiso, fwiw, but that only works with Arch Linux.

Would you want to change your distribution, or just keep Debian with some tools to automate?

Use configuration tooling such as Ansible.

You also could build a image builder to build your system. You could utilize things like docker and or Ansible to repeatedly get to the same result.

Just put your system configuration in Ansible playbook. When your distro has new release, go through your changes and remove ones that are no longer relevant.

For home, I recommend a dotfiles repository with subdirectories for each tool, like bash, git, vim, etc. Use GNU stow to symlink the required files in place on each machine.

I have the exact same workflow except I have two images: one for legacy/MBR and another for EFI/GPT -- once I read your post I was glad to see I'm not alone haha!

You might be able to script something with Debootstrap. I tested Bcachefs on a spare device once and couldn't get through the standard Debian install process, so I ended up using a live image to Debootstrap the drive. You should be able to give a list of packages to install and copy over configs to the partition.

I did the same, exactly the way you did but my "zygote" isnt as advanced.

I should make a raw ISO too, but currently I just use Clonezilla (which shrinks and resizes automatically) and have a small SSD with a nearly vanilla system.

Just because the Fedora ISO didnt boot

This is designed for Gentoo but I've used it for Ubuntu before: https://github.com/TheChymera/mkstage4/

I believe that Proxmox does this because I have installed/created containers from their available images. I wonder how they create those container images?