The NNTC Vulkan sample is working (3000+ lines of .cpp later). It supports VK_NV_cooperative_vector for decoding. So the same inference hardware the neural guys are using benefits NNTC, too. I'll have this checked into GitHub after testing on more hardware.
source & further reading
richg42.blogspot.com — original article
neural_upsampler: neural 2x upsampling as a tiny drop-in C++ library
Neural JPEG artifact reduction in C++
NNTC PBR material set compressor: now supports CPU encoding