Few days ago, it has come to my attention that Soulbringer is another one of those games that don't work with dgVoodoo and made a patch for it. Now I've upgraded the same patch to provide just a little better compatibility with ancient DirectX APIs. If nothing else, it works smoothly, setting gamma with F2 and F3 keys work, EAX executable works. GOG version for example seems to have noticeable stuttering issues, can't change gamma, EAX executable is broken. There might be a similar situation with Steam version. From the ReadMe:

This patch is intended to solve certain issues that occur on modern systems, related to game's usage of ancient DirectX APIs. It also enables the game to run via dgVoodoo DirectX wrapper. The main goal of this patch was to get the game running properly on all machines I have at home, which have graphics cards of all popular vendors (NVIDIA, AMD and Intel) and running Windows 10. The following changes have been implemented:

• Pass DDCREATE_EMULATIONONLY for DirectDraw objects used for intro cinematics, prevents the Fatal error message on startup or black screen during cinematics, depending on graphics drivers.
• Call SetAppCompatData(12, 0) in ddraw.dll to disable maximized windowed mode on Windows 8+, allows the game to run in real fullscreen mode on those systems and restores ability to change gamma with F2 and F3 keys.
• Delay execution of DllMain logic of rendering libraries to the point when the LoadLibrary call returns (startup hang prevention and dgVoodoo compatibility).
• Included registry fix which disables Windows' interfering with the game launcher. This interference can make the game crash or not start when ran through launcher under certain circumstances.

The instructions are in the ReadMe. Hopefully it works well. BTW, I've noticed that the retail version refuses to uninstall if you change the game files, so you may want to keep the backup.