Baseline (Widescreen) Solution & Issues
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
The game natively supports the most common 21:9 resolutions. Its maximum supported aspect ratio is ~2.39, meaning that 3840x1600 and 32:9 aspect ratios get pillarboxed.
A reliable workaround is setting the game to Windowed, then forcing it to be borderless with an app like Borderless Gaming or Fullscreenizer. This will remove the black bars and force the game to use the whole screen.
A less reliable workaround is having a custom resolution in the OS that exceeds that of your display. For example, selecting 3840x2160 at 3840x1080 will result in hor+ scaling, not stretching.
Eyefinity / Surround Specific Solution & Issues
Same issues and solutions as for 32:9, described above.
The HUD spanning may be undesirable in multi-monitor. Although it is minimal in this game and its importance is low, being able to see the remaining stamina or keep an eye on the FPS and latency values (if specifically enabled in the game options) could be helpful.
Some of the other UI and menu elements are also spanned.
4k UHD Specific Solution & Issues