Incorrect. That’s X11; we have that. Plan 9 is a little hard to explain quick, but I gave some examples already of stuff that is trivial with it that’s a big weird difficulty on other modern systems, but in addition to that the whole UI and the terminal / editor also work radically differently to how Unixlike systems do it.

That's most of what we do today.

Every web app you use right now - which is most of your day for most users - is just a dumb terminal UI hitting some API on some foreign computer.

Plan 9 uses the file system as a way of interacting with apis. Linux took this idea directly by copying in the/proc filesystem from 9, which are not bytes on a disk but are instead the kernel presenting its running processes in the format of files and directories in your file namespace, and with which you can interact to control those processes.

It also took this idea and created FUSE - file systems in user space - so that you can do the same thing on Linux as a user, but with not quite the same ease you have on plan 9 - and notably, fuse file systems are not naturally network file systems, and so you can't export them as easily to the network as you can with nine machines, where it's implicit.

Last, Linux took the idea of per-process namespaces from 9, setting the stage for all of the docker, snap, etc. tools we use today.

In short, a lot of nine already is mainstream because it's been adopted by Linux. However, using plan 9 and then returning back to Linux feels like putting on bulky gloves, because Linux did not start with these concepts in mind, but bolted them on after.

/Tinyrant