Vulkan is - pretty much - mantle, AMD gave everything about Mantle to Khronos, and they took it from there to make Vulkan. It does not have much to do with OpenGL apart from being its gradual successor.
And by the way, these low level APIs must be implemented by the cards manufacturers, you won't "find" more of them by looking around. See what the card manufacture say your card is compatible with, and that's that, well, apart from third party drivers.