Need a Raspberry Pi Debian image and can't (don't want to) use Raspberry Pi OS?
Download an image from https://raspi.debian.net/daily-images/ and burn it onto an SD card.
Boot into it. You will get clean minimal Debian.
Note. If you first see the boot screen and then it goes to "no signal", make sure your HDMI screen has enough power. Mine is a 7" USB-powered screen which I plugged into Raspberry Pi, and while it worked initially, this later became a problem. Feeding it from a dedicated wall charger solved the issue.
Create user pi
Log in as root without a password.
adduser pi
When it prompts for the new password, use raspberry to keep it consistent.
(At this point you should be able to ssh pi@your-rpi-ip, then su - root and continue from your computer, where you can copy and paste commands into terminal, as opposed to typing them into RPI keyboard.)
Hostname
echo 'rpi' > /etc/hostname
echo '127.0.0.1 rpi' >> /etc/hosts
Sudo
Install sudo
apt-get update
apt-get install sudo
Allow passwordless sudo for user pi:
echo 'pi ALL=(ALL) NOPASSWD:ALL' > /etc/sudoers.d/pi
chmod 0440 /etc/sudoers.d/pi
Raspi-config
apt-get install --no-install-recommends wget whiptail
wget -O /usr/bin/raspi-config https://raw.githubusercontent.com/RPi-Distro/raspi-config/refs/heads/$(. /etc/os-release && echo "$VERSION_CODENAME")/raspi-config && chmod +x /usr/bin/raspi-config