The Linux world[1] has got together and is banging out a solution for a somewhat bigger problem that the multitude of X toolkits and their different (non) approach to HiDPI.

It's called Wayland, it took some time to make and next week, new Fedora is coming out that uses it by default (until now you could "only" opt-in during login).

[1] Except Ubuntu, they have their own NIH solution, of course.

Not trying to downplay issues or shame another system, but if you compare Linux's HiDPI support to Windows, it doesn't look so bad anymore. For one, it's more likely to find apps that scale on Xorg/Wayland than on Windows, most Microsoft Windows official system apps included. Simple things like apps with list controls that have a huge number of entries where you're not able to resize the window while other more prominent MS apps waste white space like macOS and GNOME is an interesting phenomenon to observe.

X was designed for multiple DPI from the start; it was the ‘Linux world’ who abandoned everything from the ‘Unix world’ that wasn't immediately relevant to cloning the Windows desktop.

Most apps I use on Ubuntu work well on hidpi. The main problem I face is when I connect my laptop with 4k screen with some external monitor with 2k or 1080p display.