There's far, far more than Plan 9. That's only the beginning. Many others iterated heavily on Unix architectures to make them more novel, or started from scratch. John Ousterhout and U.C. Berkeley developed Sprite, which introduced things like checkpointing, live migration, SSI, log-structured file systems and other things. Andy Tanenbaum did Amoeba, which is sadly only remembered for being the platform that birthed Python. Spring was Sun Microsystems' research system, the name service of which brilliantly resolved the problem of "naming things" (I highly recommend you read this paper: https://www.usenix.org/legacy/publications/library/proceedin...). Unfortunately, Sun barely implemented any of its ideas to Solaris. Just the least interesting ones like the doors IPC mechanism.

Never had wifi.

Well, it was developed during a different time. It did get wi-fi thanks to 9front, though.

linux seccomp-bpf

A sandboxing/syscall filtering mechanism. Nothing new there, and its interface is rather leaky, much like Berkeley sockets are.

freebsd capsicum

This is one of the few legitimately interesting projects going on. Bringing capability-based security on top of fds. I don't know if it'll catch on beyond FreeBSD, though. Google seems to be an early adopter.

containerization

Nothing that IBM didn't do much better. Docker reeks of opportunism.

sendfile(), epoll() / kqueue()

sendfile(2) is just a cheap trick that got turned into a syscall: https://groups.google.com/forum/#!msg/golang-nuts/gdp1q6T0DN...

epoll(2) isn't anything special, it's a rather convoluted if performant I/O multiplexing mechanism. kqueue(2) is much cleaner designed, at least.