Valve and their open source contractors sure are a busy bunch. VKD3D-Proton, which translates Direct3D 12 to Vulkan version 2.8 is out now.
An exciting sounding improvement for lowering the CPU overhead is the addition of support for the VK_EXT_descriptor_buffer extension. On Steam Deck "most of it" was already used but now this release will allow for others to benefit too. With a note that "GPU bound performance increases slightly".
Two new extensions are now required but both should be readily available in drivers:
They have also rewritten support for host accessible images, no longer needing a bunch of per-application hacks and workarounds with Guardians of the Galaxy "finally" able to run well on NVIDIA.
On top of that there's a rewritten swap chain, which should be transparent to users but has many benefits like more precise latency control and frame pacing, reduced CPU overhead, fixes a hang in Hitman III and allows for native Linux use of VKD3D-Proton too.
Plus there's also various fixes and specific workarounds for titles like: Spiderman Miles Morales, Borderlands 3, Age of Empires IV, Resident Evil Village, Witcher 3, Gears 5 and some more minor D3D12 features were added.