Good HiDPI scaling on my external Monitor is one of the reasons i switched back to os x. For me that works very good independent of the monitor manufacturer.
Apple definitely does not "just work" in this case. They really "think different" as in different standards to ensure consumer lock-in in their walled garden.
I've tried Linux a few times in the past and it's been a mess - particularly in a mixed DPI environment. It also seems to come down to individual apps rather than the desktop manager. Not long ago I really wanted to make linux worked and so was asking questions on forums on how to make HiDPI work well, and a common response was 'no one needs HiDPI'...got it.