Vulkan is for graphics(really low level programming(meaning the dev has to do lots of things)) anyways it's like DirectX and OpenGL, it's possible that your GPU just doesn't support it, because it's a relatively a new Graphics Library. There is some chance that the dev can add OpenGL support if they want to put some more time(remember that's a hard task like i said earlier) if they're using an engine that's a big public project like: Unity/Unreal/Godot it's possible that they will release some OpenGL support very soon, if they use their own engine they will have to rewrite the engine in OpenGL.
Sorry for the broken English