I recently built a Plan 9 cluster of 8 raspberry pi zero (2w). From my supplier (digikey) the 2W was the same price and has 4X the cores!

I think it looks quite cool: https://x.com/andreer/status/2007509694374691230

Instead of having to use lots of dongles and usb ethernet, I just wired them all up using brass rods, a small 5V power supply in the base, and boot them over WiFi (just the kernel and wifi config on the sd card).

Raspberry pi's are cheap, easily available, and there is an absolutely massive trove of information about them on the internet. And the scale means that the linux implementation is very stable and "just works" to a degree that is extremely hard for other SBCs to match.

Sure, VMs are the logical choice, but not everything has to be logical. Real hardware does feel more real :-)