Open source consulting firm Collabora are certainly busy. While they work with Steam owner Valve on various things, they also work in other areas of Linux like driver development - their latest being PanVk.
Extending the Panfrost driver which currently supports OpenGL and ES across Arm Mali Midgard and Bifrost GPUs, they're now looking at Vulkan support now that Panfrost is getting quite mature. PanVk itself is already being worked on, with enough of the Vulkan API implemented so that vkcube can run but it's still overall in the early stages of development so real-world applications need more functions added and optimization is not yet a focus.
Their current plan is to merge the driver code into Mesa master once "enough features are supported and the code base is clean enough".
Fantastic to see such amazing progress all around. The more devices we have working nicely with proper 3D acceleration on Linux the better!