Baseline (Widescreen) Solution & Issues
Native HOR+ / except 4:3 is Anamorphic
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
The Game supports only 16:9 Aspect Ratio (anything else has colored Bars) - you need HEX edit the Aspect Ratio and use Borderless Gaming to get it HOR+.
HEX edit Aspect Ratio: Go to --> ...\Steam\steamapps\common\Seraph\Seraph_Data\Managed\Assembly-CSharp.dll
Look for 39 8E E3 3F and change every Instance to 60 E5 18 40.
Now run the Game in Window Mode, start a Level, Alt Tab and make it via Borderless Gaming HOR+.
Issues: Almost Perfect but the Menu is a little bit cut of.
Eyefinity / Surround Specific Solution & Issues
Same Solution as in Ultra-Widescreen but the Menu is unusable.
HEX edit Aspect Ratio: Go to --> ...\Steam\steamapps\common\Seraph\Seraph_Data\Managed\Assembly-CSharp.dll
Look for 39 8E E3 3F and change every Instance to AB AA AA 40 (3x16:9) or 9A 99 99 40 (3x16:10).
4k UHD Specific Solution & Issues