I picked up an onn box and didn't have good luck, my x265 files on Plex were choppy and the audio just says multi-channel in on my AVR. I did enable audio passthrough. Roku is useless, mine still on 11.5.
I haven't been watching this thread for awhile but just went to play a file, got the red hues, and went to see what the latest solution was.
I wanted to post here to mention that my 4802 Roku Ultra is running 12.0.0 build 4184-C2 and it DOES show the red hues. So OS 12 does not solve the problem for me.