[aaronax]

Search Amazon for "pfsense mini pc". (smile as you think about how this triggers that one pfsense guy!) Intel N100 or N150 processor, passive cooling, typically 5 1000GBASE-T or better ports, RAM and SSD included. Should be able to get one for ~$200.

[kube-system]

There are good options there, but those white label mini PCs can be hardware quality roulette.

As much as I like opnsense, I choose Ubiquiti still when I need something cheap that I need to rely on.