Device model: LG V20 Sprint (LG-LS997)
ROM version : Stock ROM (Android 7.0)
The device is explicitly branded as supporting Hi-Res audio, and has an ESS DAC (ES9218) capable of outputting it. Poweramp does not show the hi-res option, unlike the user above. I suspect this is due to differences in carrier models (The Sprint model also does not have a stock music app for some reason). UPDATE: The option not showing was due to the fact that I had the 703 build, not the 704 one:P (it still doesn't work)
audio_policy.conf
I just downloaded it, and it shows the option, but it fails and reverts to OpenSL ES immediately.