https://arstechnica.com/gadgets/2022/02/raspberry-pi-bootloader-enables-os-installs-with-no-separate-pc-required/

Setting up a Raspberry Pi board has always required a second computer, which is used to flash your operating system of choice to an SD card so your Pi can boot. But the Pi Foundation is working on a new version of its bootloader that could connect an OS-less Pi board directly to the Internet, allowing it to download and install the official Raspberry Pi OS to a blank SD card without requiring another computer.

To test the networked booting feature, you'll need to use the Pi Imager on a separate computer to copy an updater for the bootloader over to an SD card—Pi firmware updates are normally installed along with new OS updates rather than separately, but since this is still in testing, it requires extra steps.