I’ve run Kubernetes training sessions where all of the trainees had Windows laptops with VMware Workstation. I used K3S on K3OS as the guest OS at the time, and built a cluster of 3 Kubernetes servers with 2 CPUs and 2GB of RAM each, that ran a few basic workloads. I don’t see why you couldn’t do something similar on Ubuntu with VirtualBox as the vm host.

A simpler alternative might be to use microk8s or minikube on Ubuntu.

Why do you need to transfer just the internals? There are options out there that will allow you to rackmount the NUC in its case. Racknex are the best ones but MyElectronics ones might also work.