It doesn't do it well. It's inconsistently applied, many icons/apps incorrectly render, and you have to be consistent in your DE. Much like windows, even windows 10. Somehow, Apple is the only one to have actually solved this well where it just works, and apps that don't support it scale appropriately.

I run Antergos on a Macbook Pro with a HiDPI screen - with a custom compiled kernel. Things work really, really well... until I plug it into a monitor. Linux can't really deal with one screen being high resolution and another screen being 'low' resolution. Icons distort into different sizes and what not. Chrome's window decorations blow up to humongous sizes, etc. Unplugging it and having the screen readjust leaves things pretty broken. It is easier to run the Macbook screen at 1920x1080 just to not have to deal with scaling issues.

Per monitor scaling is supported by, at least, GNOME when you use Wayland.

Linux is the type of situation where apps need to opt into screen scaling. So if you have high dpi and your app isn't aware of pixel density, you'll have to squint to see anything.