Nope! Looks like I was wrong. I was never able to get it working on Gnome without the upscale/downscale workaround suggested in your link (resulting in terribly

Nope! Looks like I was wrong. I was never able to get it working on Gnome without the upscale/downscale workaround suggested in your link (resulting in terribly degraded image quality), but perhaps that is the fault of Gnome/GTK. It wouldn't have occurred to me that the fault could lie in any other layer than that which controls the resolution/DPI, but I'm certainly no expert on the Linux graphical stack.