It seems to be hot-patching the image to redirect the kernel command line to boot from the iventoy server. I booted ubuntu-22.04.2-live-server-amd64.iso and th

It seems to be hot-patching the image to redirect the kernel command line to boot from the iventoy server. I booted ubuntu-22.04.2-live-server-amd64.iso and the resulting kernel command line of the installation environment has a "url" argument that points at the iventoy server URL for the iso image. I was not able to directly boot a homegrown Debian live ISO image, so I think they just have a broad set of specific ISOs that work with iVentoy. It's not a generic "boot any ISO" solution.