UI is a layer on top of the OS.

It is not the OS.

Only on the UNIX world.

On the desktop world, the UI is a component of the OS, and is responsible of the whole OS experience.

Hence why the successful OSes that happen to have UNIX internals, those internals are not exposed to the users, and are not optional for most development scenarios.

Hence why GNU/Linux on the desktop failed, while Linux kernel on the mobile and TVs with prescribed user and developer experience has succeed.

"UNIX" should be "Posix", I think.

Not sure I agree with the last sentence, but an interesting point.

Also, to what extent is the UI part of, for example, Windows 11 ? I think Windows can run headless ?

Yes as the Server Core configuration it can, but you don't get to replace Win32 puzzle piece that goes on top with something else, you might augment it with alternative UI frameworks, but ultimately it is Win32 at the bottom layer.

Just like on macOS, while UNIX on the bottom layer, you don't get to plug something else instead of WindowServer and related low level APIs. Even with XQuartz, it builds on top of it, just like they build on top of Win32 on Windows.

> On the desktop world, the UI is a component of the OS, and is responsible of the whole OS experience.

You mean iOS when the UI sucks ? Or Android ? Or Windows ? /s

Compared with the fragmented way of UI/UX on traditional UNIX clones with special snowflakes on top of Xlib and whatever is the sound stack of the month, with exception of NeWS/NeXTSTEP/OS X, they suck less.

Linux works perfectly fine on my desktop.

Just by being in this comment section our experiences are outliers.

> we're still waiting for the year of Linux on the desktop ?

Speak for yourself. We use linux as a desktop since 1997.

Speak for yourself :)

I used linux as a desktop until about 2013, then switched to Mac OS. My linux boxes are headless now.