Baseline (Widescreen) Solution & Issues
Native, use configuration utility.
Custom resolutions can be added manually. There is no scaling of any kind, so this is mostly useful in windowed mode.
Display settings are saved in Documents\Amnesia\Main\main_settings.cfg
Some "inverted stretching" going on on 2D screens... Although the inventory looks ok in all ARs, proportions are not maintained.
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
Eyefinity / Surround Specific Solution & Issues
HUD is centered, it is worth mentioning that on the main menu the menu items are on the right monitor, but this may be a design choice, not a flaw. Only real HUD in this game is the inventory, which is centered properly.
4k UHD Specific Solution & Issues
Stereoscopic-3D Solution & Issues