Yeah but I really really don't like tools doing black magic to be honest, I'd like some documentation what it does. And if it is just cloud-init, no big deal, I already know more than I'd ever wanted about this particular piece of annoyance from wrestling with AWS, just tell me what exactly the Pi userland expects me to hand to cloud-init...
Thanks anyway for digging into the source, really appreciated!
Alas I don't know much more than that; I only remembered about the CLI bit in 1.x and went to check it was still there.
You may be able to build exactly what you want with the image generation tools, as it goes:
https://github.com/raspberrypi/rpi-image-gen
https://github.com/RPi-Distro/pi-gen
Customising the OS with pi-gen is not that bad. It's an idiosyncratic tool but it works; I've not used the newer rpi-image-gen stuff.
It feels odd to complain about "tools doing black magic" when the new way is "cloud init, a tool used by a ton of infra platforms" and the old way is "drop a file in this directory and it will somehow get slurped into the right space at the right time".