The bad news: There's no unified HiDPI solution on Linux that works well end-to-end.

The good news: You don't really need one.

Bumping the font configuration fixes 80% of the scenarios, and the rest I tweak on a case-by-case basis. The good standards-conforming apps (e.g. modern terminals, browsers, etc) automatically multiply the font sizes by your screen DPI. Most desktop managers have a scale sliders for the GUI size, if you're into that. Some stragglers include Steam which recently added support for a 2x size multiplier (it's something, but not the best).

You kinda get exposed to how the sausage is made, but the sausage still tastes great.

Linux desktop is better than it ever was, but the road to perfection is long and eternal.

HiDPI on Linux is pretty much non existent. I am telling from experience. I have booth a decent 4K external monitor and a HiDPI IPS internal display. The only setup which is ok in the sense of least horrible is Gnome mutter Wayland with experimental per monitor fractional scaling enabled. And this one is only ok if you can restrict yourself to the few ported pure GTK3 Gnome apps. Which means not that much. No Firefox. No Chrome. No Thunderbird.

And the speed of fixing HiDPI on Linux has actually slowed down.

Frnakly, and I am a hard core Linux OSS fan - come back in two years and check again.

The Linux desktop IS dead.

The biggest problem in linux is not directly HiDPI. HiDPI works (mostly).

However if you can't use wayland you will have a problem when you need the following:

Multiple monitors with different screen resultions. Lets say your laptop has 4k and you use two external monitors with 1080p than it gets tricky with older wayland or x.org. However on later stable/edge channels most things are probably better than when I tested this and I even have a colleague which has a 13" xps with ubuntu which works pretty will with its docking station.

2560x1440 doesn't even require HiDPI support really. Just increasing the font sizes is enough. The Ubuntu Unity desktop has abstracted away that in a single slider for a long time. Apparently the next GNOME version is going to go all the way and do non-integer scaling of controls as well but in my experience that's just a small benefit, just tweaking up the font sizes is more than enough.

Surprisingly, both engineers on the 2560x1440 are happy! They run Ubuntu with a second screen at their desks (27” 2560x1440 external monitors). I’m actually the one that’s unhappy because their font size is too small for me to see when pairing ;)

BTW I think 2560x1440 may not be high enough to technically be considered HiDPI?

I wish everything just used wayland and scaled correctly I am sick of having to launch chrome with an environment variable so it can run on one screen and having another instance for another. Also silly things like file dialogs not fitting. It's annoying when you look and the issues are all from years ago and still not fixed.

It's actually quite OK, with just some minor annoyances. Three scenarios for my use case:

1. Use the laptop screen only. This is easy. Just change the DPI value in my ~/.Xprofile and everything is solved.

2. Use external monitors only. Just use the default DPI value.

3. Use laptop screen in combination with external monitors. This doesn't occur hat often. But when I have to do this, there are also some ways to make it work. You can refer to https://wiki.archlinux.org/index.php/HiDPI for some reference.

- The first way is to increase the DPI in ~/.Xprofile and actually scale up the external monitor instead. I don't like this method since the external monitor just looks blurry for some reason.

- Or you can keep the DPI and downscale your internal monitor.

- Or, and this is what I do currently, use apps that support manually setting DPI in their settings, e.g. Firefox and Thunderbird, on the laptop display. You can also manually change font sizes of apps that you're going to use on the laptop display. This is a bit inconvenient but the display result will look totally natural.

I have no problems on KDE for home use, I think the problems are mixing multiple screens with different pixel densities.

Gnome has always worked pretty well with High DPI. But yes Linux display managers are generally pretty bad, as I learned with my 1440p 13 inch laptop as recently as 2015.

I have a Thinkpad P71 and I run NixOS on it. Works great with a 5k monitor, and DPI is perfect.

Most apps are written in GTK or Qt, which do scaling well.

The main issue is that scaling can't really be done on a per-display basis.