It is three scripts, sure there is some user interaction, and you do have to create and mount the image manually beforehand, but this project is still in early development and hopefully some issues will be ironed out in the future.
There is one major issue, however, and it impacts greatly if you want to switch SD cards from one Pi model to another: the images are not universally compatible with the other Pi generation. So a Pi 3 image will not run on the Pi 4 and vice versa. By default, the script sets up the image for the Pi 4, but tweaking stage1.sh you could change to a Pi 3 image instead. The Pi 3 image works on all Pi 3 models (3B, 3B+, 3A+) but not on the 4. I am looking for a fix for this.
On the GitHub releases page for this project are two images made with this script, both complete with a basic Debian installation and most stuff working, including WiFi. There is no desktop environment, but one can easily be installed. The stage2 script has commented out a line to install the XFCE desktop with preloaded software, which can be uncommented or changed to install another DE.
Turns out the Pi 4 image won't boot without renaming the kernel8-rp4.img to just kernel8.img, will be fixed in next image release, will update script soon to incorporate this fix. However, with the modification the image will work perfectly, much smoother than on the Pi 3. With fake_kms enabled in config.txt, the Pi 4 gives a smooth Debian experience with graphics acceleration.
Anyways you can find the GitHub page here and the releases section here. Enjoy!
Username is debian, password also debian.
PS: Credit to sakaki- for her prebuilt kernels used in the script and image. (Link 1) (Link 2)
