To install:
Place d3d9.dll in the game folder. Usually this is C:\Program Files (x86)\Steam\steamapps\common\Sonic & All-Stars Racing Transformed\

Notes:
* The Steam overlay does not work (currently)
* This fix may offer a performance boost, even for people not using NVidia 16/20 series cards!
* This d3d9.dll file is part of the DXVK project, which translates DirectX 9 to Vulkan. More info here: https://github.com/doitsujin/dxvk