FIX THE PROBLEM APPLE SCUM! I DONT WANT TO BUY A NEW MONITOR JUST BECAUSE OF THIS! I WANT TO BE ABLE TO SEE THE UI AS HIDPI ON MY 2K DISPLAY OR CREATE CUSTOM RESOLUTIONS THAT CAN HAVE HIDPI OPTIONS ENABLED! APPLE DONT BECOME TRASH YOU CAN DO THIS ON WINDOWS AND SET THE UI TO 125% WHAT THE HELL IS WRONG WITH YOU PEOPLE

Please somebody file a lawsuit for this issue already! Apple deserves to be sued and humiliated for blocking us from using HiDPI on QHD displays even with 3rd party workarounds that have existed for years! Disgusting apple! SOMEONE PLEASE SUE THEM ASAP

I have done it! I got HiDPI working on my mac mini connected to a benq 2k monitor. I've got options of 720p, 1080p, 1440p HiDPI and more. I had to buy a dummy hdmi plug costing about $10. Then created a startup resolution of 1920 x 1080 with scaled base at 3840 x 2160 on switchresX. That enabled HiDPI options on the dummy plug and now I'm mirroring that to my mac mini's primary display. At least now I don't have to spend $500-1000 on a new display.

This is issue is resolved for mac mini users with a simple <$10 dummy plug like the one below

I demand a statue be erected in my honour for this very solution