I use KDE on 4K at 200% too. On FreeBSD with X even, at the moment :) Though for work I use Linux with Wayland. It's true that the mouse doesn't auto scale but

I use KDE on 4K at 200% too. On FreeBSD with X even, at the moment :) Though for work I use Linux with Wayland. It's true that the mouse doesn't auto scale but you can manually make it bigger in settings. Same with the "taskbar" height. HiDPI is still a bit in development and I heard the next release 5.23 will bring a lot of goodies in October. But overall I think it's fine.. Where it falls down is mixed DPI (e.g. one screen at 200% and another at 100%). But even Windows is still very flakey with that. Only macOS covers that scenario perfectly. One thing I love about KDE is the wealth of options. Gnome is heading the way of Apple: opinionated software and minimalism. Windows is heading the same way though not as strongly. That doesn't suit me. KDE is really my thing.