Another alternative is to use Ubuntu server for the RPi instead of Raspberry Pi OS. Ubuntu server includes support for cloud-init which can be used for initial configuration.
That's true. Are there any other advantages to using Ubuntu over Raspberry Pi OS? Most of my projects run headless and take advantage of the GPIOs / built in camera. Does Ubuntu support those features well too?
Ubuntu does support using both the GPIOs and camera. I use Ubuntu other places so the advantage it gives me is familiarity. I can manage my RPi's just as I do my other systems. Also although there is a lot of Rsapberry Pi documentation available there is even more for Ubuntu and it applies to the RPi version.
If, like me, you've a few Raspberry Pi projects and need a standard way to create your base images before first boot then this CLI tool might be for you. So far, I've only tested with a couple of scenarios and the tool has worked very well. I still have to play with using a Custom Phase Script to set up custom drivers / non-standard packages. I'm confident it will work flawlessly. Very impressive IMHO.