In the official Kali Linux website, you can download the ROM for free. Installing Kali Linux on an Android device without rooting is possible in numerous ways. Kali netnunter supports both unrooted and rooted devices and can be installed on any Android device easily in a matter of seconds. Kali nethunter is the most popular open-source penetration tool, offering support for Software Defined Radio (SDR), 802.11 Wireless Injection, AP mode, a complete Linux Setup, and USB Y-cables and HID Keyboards integrated.
Are you trying to figure out how to install Kali Nethunter on an Android phone without root using Termux? If so, you are on the right page.