Irix DE it's just a tweaked MWM and Motif tools. Nothing you couldn't get with EMWM, XMToolBox for the menu and some additions.

https://fastestcode.org/emwm.html

No vector icons for XFile, but at least you can set SGI-like ones once you extract the TGZ in the correct place.

And some tools like the Fluxbox-Blackbox like slit from this guy:

https://luke8086.dev/netbsd-on-thinkpad-380z.html https://github.com/luke8086/pmdock

Yeah, but I am speaking about the out of the box experience, and culture of people using those systems, not the do your own distro kind of thing that nowadays plagues Linux.

Or all the other UNIX clones that were basically UNIX System V (or BSD derived) + twm, latter CDE, with the only visible difference being the vendor's name.