It's hardware-accelerated paravirtualization. You can't just use that inside an arbitrary VM. Every layer (hardware, host OS, every guest OS but the last in the chain) has to support 'nested virtualization', and you have to enable/configure it.

On Linux, this project doesn't require nested virtualization. On any other operating system, it does. In that way, the host OS ends up mattering.

Docker Desktop makes me wanna scream.