Commenting on an issue on the Vulkan-Ecosystem GitHub page, an NVIDIA developer has mentioned how transform feedback support will come to Vulkan.
From what I understand, some DirectX games use it and Vulkan currently has no support for anything like it unless developers write their own workarounds. This is especially important for projects like DXVK which Valve's Steam Play uses, because it's translating DirectX calls into Vulkan and so it can't exactly ignore it.
Here's what the fellow from NVIDIA said about it:
Some members of the Vulkan working group are developing a multi-vendor EXT extension for transform feedback with the primary goal of satisfying the needs of the DXVK, vkd3d and ANGLE translation layers. The Vulkan working group does not plan to promote this functionality as a KHR extension or as core functionality because it believes there are better, more forward-looking ways of processing and capturing vertex data with the GPU. The multi-vendor EXT extension should be available soon and is likely to be implemented on those platforms where DXVK, vkd3d and ANGLE translation is required.
In the end, this should hopefully mean that DXVK and Wine or Valve's Steam Play can support more games on Linux. To give you an example of it, the developer of DXVK teased this screenshot in our forum of The Witcher 3 (a Windows game) running on Linux with DXVK with some graphical issues fixed.