There was Plan9. But the people who worked on that, who are bitter that nobody uses it, or anything like, or even anything "post unix", don't realize what the killer feature of linux was, which ended "OS research":
It was the large body of useful open source and copyleft code. This made it so everyone could stop pouring huge resources into the base OS layer individually, use something that works really quite well (with whatever necessary tweaks since it is open source), and focus on what goes on top. And there's no one extracting rent on this layer. There's no licenses and activations. Nothing of the sort. (You can contract for RHEL, but you can just as easily not.)
BSDs came a couple of years after linux, and plan9 was open sourced many years after (and initially under the problematic "lucent public license"). It was way too late. And the innovations to the most basic interfaces of the OS were just not nearly as valuable as the body of open source which was already available for Linux / BSD.
Plan9 is like the Concorde - pinnacle of tech/design, nobody uses it. Never had seat-back entertainment. Never had wifi. Maybe a silly metaphor, but it fits the OP.
There are still low-level changes these days in Linux and BSDs. Nothing that drastically breaks compatibility of course. But more security boundaries and privilege management (openbsd w/x and aslr stuff, linux seccomp-bpf, freebsd capsicum, containerization), and speed/efficiency measures like sendfile(), epoll() / kqueue(), RCU fs cache lookups, etc.
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.
It was the large body of useful open source and copyleft code. This made it so everyone could stop pouring huge resources into the base OS layer individually, use something that works really quite well (with whatever necessary tweaks since it is open source), and focus on what goes on top. And there's no one extracting rent on this layer. There's no licenses and activations. Nothing of the sort. (You can contract for RHEL, but you can just as easily not.)
BSDs came a couple of years after linux, and plan9 was open sourced many years after (and initially under the problematic "lucent public license"). It was way too late. And the innovations to the most basic interfaces of the OS were just not nearly as valuable as the body of open source which was already available for Linux / BSD.
Plan9 is like the Concorde - pinnacle of tech/design, nobody uses it. Never had seat-back entertainment. Never had wifi. Maybe a silly metaphor, but it fits the OP.
There are still low-level changes these days in Linux and BSDs. Nothing that drastically breaks compatibility of course. But more security boundaries and privilege management (openbsd w/x and aslr stuff, linux seccomp-bpf, freebsd capsicum, containerization), and speed/efficiency measures like sendfile(), epoll() / kqueue(), RCU fs cache lookups, etc.