Yes, any Envy can handle 4:4:4.
EDIT: Let me add some more info to that. In the following a quote from the developer from back early 2022. The Envy does full 4:4:4 processing since the very beginning:
"Pipeline bitdepth is an interesting topic. A pipeline can use either integer or floating point math, and you can have a pipeline in either 4:2:2 or 4:4:4, and you can count bitdepth either per component or per pixel. Envy's pipeline is full 4:4:4, from start to finish. If the input signal is 4:2:2 or 4:2:0, Envy always upscales chroma to 4:4:4 in the first step, usually using AI chroma upscaling. If you want to see some bitdepth per pixel numbers, here you go:
8bit per component 4:2:2 = 16bit per pixel
10bit per component 4:2:2 = 20bit per pixel
12bit per component 4:2:2 = 24bit per pixel
16bit per component 4:2:2 = 32bit per pixel
16bit per component 4:4:4 = 48bit per pixel (Envy temporary buffers)
32bit per component 4:4:4 = 96bit per pixel (Envy calculations)
It could be argued that the bitdepth only needs to be high enough to not introduce any banding (or other) artifacts, so maybe Envy is going overboard here. But that's just the native bitdepth Direct3D GPUs are working in, so it doesn't cost us anything. Now if you'd ask me how many bits a video processing pipeline needs to have, I don't really know. But surely it doesn't hurt to be on the safe side."