Devterm CM3 ubuntu server image

ubuntu-21.04-preinstalled-server-armhf+raspi.img

Prepare

Edit /boot/cmdline.txt and /etc/fstab of this img
/boot/cmdline.txt

console=serial0,115200 console=tty1 root=PARTUUID=78e1086a-02  rootfstype=ext4 elevator=deadline rootwait fixrtc splash

/etc/fstab

PARTUUID=78e1086a-02   	   /         ext4   discard,errors=remount-ro       0 1
PARTUUID=78e1086a-01       /boot/    vfat   defaults        0       1

Enter chroot

sudo losetup -P /dev/loop10 ubuntu-21.04-preinstalled-server-armhf+raspi.img
sudo mount /dev/loop10p2 /mnt/p2
sudo mount /dev/loop10p1 /mnt/p2/boot
cd /mnt/p2
sudo mount --bind /dev dev/
sudo mount --bind /sys sys/
sudo mount --bind /proc proc/
sudo mount --bind /dev/pts dev/pts

sudo chroot .

Inside chroot

sudo apt remove linux-image-raspi linux-image-5.11.0-1007-raspi -y
sudo apt install net-tools network-manager -y

wget -O - https://raw.githubusercontent.com/clockworkpi/apt/main/debian/KEY.gpg | sudo apt-key add 
echo "deb https://raw.githubusercontent.com/clockworkpi/apt/main/debian/ stable main" | sudo tee -a /etc/apt/sources.list.d/clockworkpi.list
sudo apt update && sudo apt install devterm-thermal-printer devterm-keyboard-firmware devterm-fan-temp-daemon-rpi devterm-thermal-printer-cups devterm-kernel-rpi devterm-audio-patch devterm-backlight-rpi -y

sudo bash -c 'cat <<EOF >/etc/lightdm/lightdm.conf.d/99-cpi.conf 
[SeatDefaults]

greeter-setup-script=/etc/lightdm/setup.sh
EOF'

sudo bash -c 'cat <<EOF >/etc/lightdm/setup.sh
#!/bin/bash
xrandr --output DSI-1 --rotate right
exit 0
EOF'

sudo chmod +x /etc/lightdm/setup.sh

sudo bash -c 'cat << EOF > /etc/X11/Xsession.d/100custom_xrandr
xrandr --output DSI-1 --rotate right
EOF'

sudo reboot

sudo apt-get install tasksel

Outside chroot

sudo tasksel to select desktop env