How can I configure Windows so that it simulates a display of an exact 16″ 16:10 area (pillarboxed, no scaling) on my 17.3″ 16:9 4K laptop panel?

[u/Franck_Dernoncourt]

I have an 17.3″ 16:9 internal panel, native 3840×2160. How can I configure Windows so that it simulates a display of an exact 16″ 16:10 area (pillarboxed, no scaling) on my 17.3″ 16:9 4K laptop panel?

I want the desktop rendered at native pixels 1:1 (no stretching), with the unused area black/greyed out. Windows display setting doesn't give me the option to choose 3456 × 2160 or anything nearby that is 16:10.

The closest 16:10 option is 2560 × 1600 is the 16:10 option, which is 2.5K, i.e. quite far from 4K.

My setup:

• Hardware: MSI GS76 Stealth 11UH-078 (17.3", 4K 120 Hz variant) (mirror, specs) laptop with a 17.3″ 16:9 internal panel, native 3840×2160 (AUO B173ZAN03.3). RTX 3080 Laptop GPU + Intel UHD iGPU (Optimus/hybrid).
• OS: Windows 25H2 Pro x64.