It’s the fractional scaling required for all the other resolutions in between which is troublesome, and I believe that applies to Macs too.
In this space, I think the only contender doing it really well is Microsoft Windows.
That said, I prefer Linux. For me having a few warts here and there is an perfectly acceptable price to pay for having a full computing environment I can fully trust and adapt to my needs.
Not if you have a secondary monitor that doesn't need doubled, e.g. laptop built-in 4k with a 1920x1080 external. As far as I know this is an X problem.
Not if many apps don't have, and will not soon get, double-density assets.
(I'm a high dpi screen user)
Was responding to the argument that it works just as good as in MacOs though -- where companies were swift to change assets.
So for example a MacBook Pro with a native resolution of 2880x1800 and native effective 2x of 1440x900 can also run at effective 1680x1050 or effective 1920x1200. This works on external displays as well.
Windows has been getting better but it's still not brilliant, even with resolution independent frameworks like WPF there are a ton of issues.
Ubuntu/Gnome was completely broken for me when I tried it last year. KDE was the best of the desktops but still not as good as MacOS.