Install raspian OS lite with the rpi-installer. Use for the settings

• ssh enabled
• use a unique host name for your device
• use the host name as username
• use a unique password. Store username and password at a safe place

After installation and first boot, log in via ssh

Install missing packs

sudo apt update && sudo apt upgrade 
sudo apt-get install --no-install-recommends xserver-xorg x11-xserver-utils xinit openbox python3-tk git lightdm

For the display driver, follow the instruction from https://joy-it.net/en/products/RB-TFT3.5, which are

git clone https://github.com/goodtft/LCD-show.git
chmod -R 755 LCD-show
cd LCD-show/

Depending on the display size, use

sudo ./LCD32-show

or

sudo ./LCD35-show

After reboot and relogin, do

sudo raspi-config

Go into System Options/ Boot / Auto Login. Select Desktop Autologin to start the window manager at boot

Add the following commands to /etc/xdg/openbox/autostart

# Disable any form of screen saver / screen blanking / power management
xset s off
xset s noblank
xset -dpms

# Allow quitting the X server with CTRL-ATL-Backspace
setxkbmap -option terminate:ctrl_alt_bksp

Append the following lines to ~/.bashrc

###  start the xserver at startup  ###
[[ -z $DISPLAY && $XDG_VTNR -eq 1 ]] && startx -- -nocursor

Clone all needed libraries, e.g. pyUMenu

cd
git clone https://github.com/stko/pyUMenu.git
git clone all_the_others...

Create and activate a python virtual environment in your final application directory, here e.g. pyUMenu

cd pyUMenu
python3 -m venv .venv
source .venv/bin/activate

Add the cloned libraries to your virtual environment

pip install -e ../my_library
pip install -e ../all_the_others...

Add your program to the openbox autostart by nano $HOME/.config/openbox/autostart like eg.

cd $HOME/pyUMenu
.venv/bin/python pyumenu_demo.py

After finishing and testing, make the system read-only with raspi-config

To be descripted here

If needed, the touchscreen can be calibrated

sudo apt install xinput-calibrator

run it:

DISPLAY=:0 xinput_calibrator

copy the generated output into

sudo nano /etc/X11/xorg.conf.d/99-calibration.conf