Get a Raspberry Pi WH and a Waveshare 4inch DPI LCD and assemble them
Download an old version of Raspberry Pi OS Buster, I used this one: https://archive.org/details/2021-05-07-raspios-buster-armhf
Install IMG with Raspberry Pi Imager, and set up SSH and Wifi.
After finishing saving to the SD card, re-mount it to your computer and copy the files in 4DPIC-DTBO.zip to the /boot/overlays folder (Downloaded from https://www.waveshare.com/wiki/4inch_DPI_LCD_(C)) and then open the file config.txt from the SD card's root folder and add the following to the end of the file
gpio=0-9=a2
gpio=12-17=a2
gpio=20-25=a2
dtoverlay=dpi24
enable_dpi_lcd=1
display_default_lcd=1
extra_transpose_buffer=2
dpi_group=2
dpi_mode=87
dpi_output_format=0x7f216
dpi_timings=720 0 46 2 42 720 0 16 2 18 0 0 0 60 0 60000000 6
dtoverlay=waveshare-4dpic-3b-4b
dtoverlay=waveshare-4dpic-3b
dtoverlay=waveshare-4dpic-4b
Start the raspberry pi, the screen should turn on, wait until it has connected to WIFI and then use SSH to connect to it
Update everything with sudo apt-get update && sudo apt-get upgrade -y and then sudo apt-get install unclutter to hide the mouse cursor
Edit the file sudo nano /etc/xdg/lxsession/LXDE-pi/autostart and add this to the end (update to your URL)
@unclutter -idle 0.1 -root
@xset s off
@xset -dpms
@xset s noblank
@chromium-browser --no-sandbox --disable-infobars --noerrdialogs --incognito --check-for-update-interval=1 --simulate-critical-update --kiosk https://yoururlhere.com
Reboot with sudo reboot and everything should work!