Hello, I was wondering how to let the user choose the graphics API they want to use. Right now I have some players with older machines that are having trouble with DirectX and Vulcan but OpenGL works fine. Right now I only have the game running in OpenGL, but I would like to have the options for users to pick Vulcan or DirectX if they so choose.
You can using a command line argument. See this: https://docs.unity3d.com/Manual/CommandLineArguments.html
No, just create a build with all graphics APIs present, and then make a wrapper app that displays graphics API options for your game and then launch your game with appropriate command line arguments from it.