You know, in 5 years, many things changed.

What's wrong with 4k monitors? I'm typing this on Fedora machine with one (default install with no tinkering, Gnome on Wayland).

High-DPI is still a mess on Ubuntu (and Debian, for that matter). Last time I used Ubuntu on a 4k panel I had to manually edit some xorg config files. I'm using Debian+KDE right now and I had to manually make some adjustments (in a UI, at least) and it still randomly gets confused sometimes.

Not true for me. I've used several distros (including Ubuntu) with Gnome on my 4K XPS and the worst I've had to do is go into Gnome settings and click 200% GUI scale. I'm pretty sure Ubuntu set that automatically.

High DPI is fine as long as you have just one display. However, there's no good way to have one high-dpi display and one normal one (for example, a laptop with high dpi screen connected to a standard external monitor).

There is a good way to have mixed-dpi setup: you use Gnome-on-Wayland (for normal users who expect normal desktop) or Sway (for those who want tiling wm).

Mixed DPI is not coming to X11 displays. If you insist on X11, you are going to have bad time.

Not to mention mixed-DPI. Apple is the only vendor who actually handles HiDPI and mixed-DPI environments really well in my opinion.

macOS can scale different parts of an application differently depending on which screen it is on. So if you are in the process of moving an application from one screen to another, it doesn't change size mid-move.

Windows can't do that, and I've even seen applications where all windows belonging to an application use the same DPI (chosen based on which window is in focus), regardless of the DPI of the screen the window itself is on.

So it seems to me the integration of mixed-DPI into window rendering APIs was not well handled by the development team behind its implementation in Windows.

The most common "solution" I see is lowering the resolution of the high-DPI display, but that's not a solution, that's actually not even a workaround, it is literally removing the problem by pretending my screen is not as good as it is.

4K support seems to vary a bit from distro to distro. Some are good, some are lagging.

I'm using Linux with 3x 4k monitors at work. I set the scaling to 150% and it just works. I'm using Awesome WM.

If all your monitors are 4k it works, but if you have a mix of high dpi and standard dpi monitors it does not work. And I'm betting you can't share just one of those monitors with any screen sharing software. Something I need to do frequently.

Sharing a window may work and amount to the same thing. Depends on the software perhaps.

Two 4k monitors here on Ubuntu Mate, works great. Shared my screen last week.

External monitor support on macOS is terrible. When it does work, you can't turn on HiDPI resulting in a tiny UI. And the latest 16" macbooks simply kernel panic: https://discussions.apple.com/thread/250876794

It sucks that you are having issues with your setup, but in general macOS is the king of external monitor support.

Compare the experience with Windows for example, where disconnecting from your external monitors pushes all applications and windows to the remaining monitors, and doesn't restore them when the external monitor is reconnected.

macOS also handles mixed-DPI really well, no other vendor even comes close, Windows simply scales according to the monitor most of the application window is on, resulting in ugly resizing of applications when moving from one monitor to another.

I don't know what you're talking about with regards to "turning on HiDPI", can you elaborate?

By "turning on HiDPI", I mean having access to a menu such as this https://miro.medium.com/max/3518/1*QXxPDSp60XIZJhz4isSpiw.jp... Without the ability to scale the UI, this is what part of the UI of Xcode looks like on a 4k monitor: https://imgur.com/a/beTxJNG It's unreadable.

> Compare the experience with Windows for example, where disconnecting from your external monitors pushes all applications and windows to the remaining monitors, and doesn't restore them when the external monitor is reconnected.

Huh? I have a dock that I disconnect and reconnect from all the time; windows move onto my laptop screen when I disconnect, and move back onto my docked screen when I reconnect.

Do you have multiple screens active at one time? This is really only a problem when you have multiple screens, applications don't "remember" which screen they are supposed to be on, they just go to the "primary" screen when docked.

Ah, you're right. I do use the dock screen and the laptop screen, but hadn't noticed that everything moves to the dock screen even if it was previously on the laptop screen when docked.

Does System Prefs > Displays > Scaled not work?

HiDPI is working fine on my 3 external displays