Great to hear that driver version 512.96 also fixes this for you!
No idea where we could also report this issue. Don´t know if the mpv github repo is the right place or if nvidia just screwed it up…
Exactly, this was also discussed in this thread => [HDR Metadata Passthrough] - Plex HTPC for Windows
The refresh rate build found here => [HTPC] Testing Windows HDR Switching also has a workaround for the vulkan stuck in hdr bug.