Does not work on 4K display, works only with resolution 1280x800 with HiDPI about betterdisplay

[Miliardi]

SAMSUNG:
Resolution: 2560x1440 (QHD/WQHD - Wide Quad High Definition)
UI Looks like: 1280 x 720 @ 60.00Hz
Framebuffer Depth: 30-Bit Colour
Main Display: Yes
Mirror: On
Mirror Status: Master Mirror
Online: Yes
Rotation: Supported

[Miliardi]

Is it possible to make UI look like 1080p?

[waydabber]

Yes, you should enable flexible scaling and set the resolution to 1080p HiDPI. https://github.com/waydabber/BetterDisplay/wiki/Fully-scalable-HiDPI-desktop

[Miliardi]

Flexible scaling is a premium future. And you app doesn’t work at all as is except 1280x720 HiDPI

Is there any way I can make sure it works? Or do I need to buy the Pro version to see it doesn't work anyway?

I tried to add custom resolutions both my target one and twice as low to get 2x HiDPI but they all looks like lowDPI.

[waydabber]

I can't be sure about what you see of course but if you create an 1920x1080 custom resolution which is available in HiDPI and select that mode, then if the display can otherwise properly output 2560x1440 then the image should be a 3840x2160 resolution desktop (logical 1920x1080) scaled down to 2560x1440. It will of course look somewhat pixelated still due to the low PPI of the display (if it's a 27" one) but quality should be improved compared to 1920x1080 LoDPI.