Here you can find ready-made PiKVM images for Raspberry Pi

Download the appropriate memory card image for the PiKVM. Select the image by the board, platform, and the video capture device you are using.

Minimum 16 Gb memory card class 10 is strongly recommended.

Raspberry Pi 4, v2 platform:

Raspberry Pi Zero 2 W, v2 platform:

Raspberry Pi Zero W (legacy), v2 platform:

Raspberry Pi 4, v3 HAT platform:

To flash the image follow the instructions.
Right now, pre-compiled images are only available for the Raspberry Pi 4 and Zero (2) W. In all other cases, you will need to build the operating system yourself. But don't worry, it's very simple.
Images archive.