Initially I needed a lab to practice deploying & upgrading & disrupting on-prem talos linux for k8s, and design benchmarks around it. So 4 machines does that. The zimaboard in front with pfsense (which is a PITA by itself) and nginx is a good way to make it pick-up-and move (ie. internal networking config). For <£2k the set up is very cheap for what is being tested. It meant I didn't have to go and sit on the other side of a security checkpoint for most of the work. It was cool to keep around as its trivial to make the lab guests unable to see my home network and vice-versa.

Now I often have the 4 k8s hosts off. But use them maybe once a month.