Instructions see below
For the Raspberry Pi 4 B there are now a wide range of TFT displays available. This was made possible by the "Linux Framebuffer driver for small TFT display modules" by notro. In the past this driver had to be installed in the kernel itself, but today it is integrated in the kernel or the display manufacturers offer a ready Raspian IMAGE for the microSDHC memory card.
A good guide can be found on the Raspberry Pi website: Installing Operating System Images
In short: Download + Unzip + Check with "df -h or fdisk -l" which DEVICE name the Micro SD card has and write it:
dd if=2021-01-11-raspios-buster-armhf-lite.img of=/dev/sdX 2.1 GiB [========================================================>] 100%
pi@raspberrypi ~ $ git clone https://github.com/waveshare/LCD-show.git pi@raspberrypi ~ $ cd LCD-show/ pi@raspberrypi:~/LCD-show $ sudo cp ./waveshare4c-overlay.dtb /boot/overlays/waveshare4c.dtbo pi@raspberrypi:~/LCD-show $ sudo cp ./waveshare4c-overlay.dtb /boot/overlays/ pi@raspberrypi ~ $ sudo nano /boot/config.txt #Waveshare 4.0 [4inch_RPi_LCD_(C)] dtoverlay=waveshare4c:rotate=90