Richard Miller's port of plan9 runs on every RaspberryPi (pi0 to pi3 - where it uses all the cores). This may be the easiest way to experience plan9 and to build a small distributed system. You can experiment with device drivers or do other kernel hacking fairly quickly -- compiling p9 kernel from scratch takes about a minute on a 'Pi. This is good enough if you just want to play with plan9. You need not bother with an x86 system unless you want to use plan9 as your main system or for some serious work.