Those with a Hi-DPI *nix setup, what desktop are you using?

(OP) I have two setups: a desktop which isn't Hi-DPI and a laptop which is. I like to keep the same thing running on both, and at the moment I use Cinnamon (which has been my go-to for a while now), although I've replaced a number of the default Cinnamon applications with MATE's equivalents (e.g., xreader to Atril because of xreader's weird behavior with left and right arrows not going through pages).

I've had some mind to change in the recent past. I don't really want to go to GNOME because I enjoy the traditional desktop model. MATE has some quirks I don't love and XFCE is still not great for scaling (though has gotten a lot better recently). KDE, meanwhile, might be promising, but I have a strong distaste for their default aesthetic (though I am sure I could change it to fit my needs more). I'll have to experiment in the near future.

32 inch 4k LG monitor: I use i3 window manager and just set "Xft.dpi: 144" in "~/.Xresources".

KDE, it has good support for High-DPI and using it with two screens with different PPI ratios, like a 3k laptop display and large external 4k monitor. Gnome still only supports integer scaling (well fractional scaling is in beta but it's still very broken). I heard good things about Xfce as well.

KDE. Don't bother with fractional scaling though.

If 2x isn't the natural scaling for your monitors, set the toolkits to 2x anyway and then using xrandr to render into a larger buffer that is scaled down to the "effective" resolution you're looking for. This is basically the same approach macOS uses.

It also works on GNOME, there's nothing KDE-specific about it.

For example, my X1C6 has a 2560x1440 resolution, but the effective resolution I'd like to see is 1600x900:

xrandr --output eDP1 --fb 3200x1800 --panning 3200x1800 --scale 1.25x1.25

I have 27" 4K monitors hooked up to my desktop that I use the same approach with, but rendered into a 5120x2880 buffer and scaled by 1.33x1.33.

I use i3, and just adjust the mode (resolution) with one of the available ones listed by xrandr:

Like this:

    xrandr --output HDMI-0 --primary --mode 2560x1440

If I want bigger text on my console I might use 1920x1080.