You used to also be able to get the opposite; one Linux kernel with a unified userspace distributed across a cluster.

https://sourceforge.net/projects/kerrighed/

That's cool! Similar is the idea of running a single large VM across multiple hosts. There have been several iterations of that idea, the latest being a presentation at this year's KVM Forum: GiantVM: A Many-to-one Virtualization System Built Atop the QEMU/KVM Hypervisor - Songtao Xue, Xiong Tianlei, Muliang Shou https://kvm-forum.qemu.org/2025/

I wonder if modern numa-aware software could take advantage of this if the Linux APIs report the correct topology.