Pi 5 3.5″ Touchscreen Setup

I have a 3.5-inch capacitive display (320×480, ST7796S driver with FT6336U touch controller) that I want running flawlessly on a Raspberry Pi 5 under the latest Raspberry Pi OS. The goal is simple: when I power up the board I should see the full desktop rendered on the screen, and every on-screen control—from menu bar to file manager to browser scrollbar—must respond to touch just as it would to a mouse.

What I need from you
• Device-tree overlay or other kernel-level configuration that loads the ST7796S framebuffer and FT6336U touch modules at boot
• Correct rotation, resolution, and back-light settings so the desktop fills the panel without distortion
• Calibration or mapping that lines the touch coordinates up with the GUI (no dead zones or offset taps)
• A concise, reproducible guide or script that lets me recreate the setup on a fresh SD card in minutes

Acceptance criteria
1. Booting Pi OS shows the desktop on the 3.5″ screen automatically.
2. Tapping any standard UI element launches or selects it reliably.
3. Multi-window dragging, scrolling, right-click (press-and-hold) and on-screen keyboard work without additional tweaks.
4. Your instructions or image build cleanly on a stock Pi OS install for Raspberry Pi 5.

If you prefer, you can supply a ready-to-flash SD-card image; otherwise a step-by-step shell script or Ansible playbook is fine. I can test over a remote session and provide prompt feedback.