> windows should be square

found the Windows 8 enthusiast! haha, I kid. (I myself use a tiling window manager , i3, with completely square windows without any gaps or rounding)

Haha, Windows had square windows long before 8.

If I could run the Windows 2000 UI on a modern OS I would but any recent clone/theme/etc feels too uncanny valley.

My custom XFWM theme has square corners on windows without focus and large-radius rounded corners on the one window with focus.

The square corners are part of a 2 pixel wide border (one black, one white) because who needs to waste space on handling things we aren't manipulating? But the title bar is high-contrast, because you'll go looking for it when you want to switch windows.

The round corners go with a fairly thick border in a customizable color, usually something very bright in the yellow, orange or cyan ranges. When you sit down, you should immediately know what is active.

I like rounding the corners on i3. It is a bit wasteful but the base WM is so efficient with my pixels that I have some to spare.

Not having i3 is truly the worst part about Macs.

(Yes, please tell me about some buggy half-compatible tiling window manager for my Mac.)

For real. Doesn't help that the three/four finger swipe between full screen windows/workspaces has a mandatory animation that you can't disable (you can turn on "reduce motion", but it simply changes the scrolling animation into an equally time-wasting fading animation).

Surely MacOS has some nice virtual machine that you could run Linux in?

Virtual machines aren't the solution for day-to-day computing though. You're missing out on the graphics acceleration, being able to plug things in that just work, and so on.

If you're running your UI on a Linux VM....why not just used Linux?

UTM.

You were being sarcastic, but aerospace is100% worth setting up