Inspired by this post on ipxe.org, the following script downloads and extracts the current Debian Bullseye netboot installer kernel and initrd, and prepares them for usage as a rudimentary disk image writing utility. It is intended to be used for KVM virtio guests on Proxmox VE, to install Mikrotik RouterOS via network boot.
Appropriate iPXE commands to use the resulting kernel and initrd would be something like the following: