Yeah, I agree OSD volume works. Not tried the other option you mentioned, but "Display" does not, nor does the OSD menu, at least to a LG OLED.
Handshakes depend on exactly what is in the chain. DV is the same as HDR10 and switching back to SDR here. It's fine, but definitely a couple of seconds, not instant. But I have a 15M Hybrid Fiber cable to the display, my old "pure fiber" Celerity cable was noticeably slower, but again for all mode switches.
Edit: Done a bit more testing on this and I think a fair summary is on-screen "confirmation messages", e.g. volume or changes of DSP mode, work - they are overlayed on DV video, other options like the on-screen menu and the full screen info overlay you get by pressing the display button blank the video while they are on screen.
LG OLED65E6V, Yamaha RX-A3060 AVR, Oppo UDP-203 UHD Blu-ray player, Apple TV 4K, Sky Q 2TB, Chromecast Ultra
Home-built Ivy Bridge i5-3570K HTPC, 8GB RAM and Nvidia GTX1050 GPU with Plex and Jriver Media Centre,
Ruipro 15M Fiber HDMI cable, B&W FPM speakers, Logitech Harmony Ultimate intelligent remote.
Last edited by jong1; 03-13-2018 at 08:13 AM.