The Roku Ultra 2020 played my 24-bit 96Hz and 192Hz stereo music files. It also played my only 24-bit 96Hz 5.1 (6 channels) music file, but output was transcoded in stereo only.
This was played with the Roku connected first to Android TV, then from TV to Denon AVR via HDMI ARC, and it was the same when I then connected the Roku first directly to the Denon. The 5.1 flac still showed up as Stereo on the Denon. I used the Roku Media Player with USB drive connected and also streaming (DLNA) same file from my NAS.