macOS and Windows have a much smaller set of variants, and tend to ship a single UI with everything included with OS. Even the best single desktop Linux distros will ship divergent KDE and Gnome apps.

If you want essentially perfect high-DPI support out of the box and can afford higher end displays, use macOS. It just works. I see the comments above about scaling, and to that, I say: most people will never notice. However, a Win32 app being the wrong scale? They'll notice that.

But the real display weak point of Linux right now vs Windows is HDR for gaming. That's a real shitshow and it tends to just work on Windows.