I use my Ultra 2018 (4660x) with my Onkyo (TX-NR509) pretty seamlessly using auto for both audio and video (1080p detected and auto on audio). The software on the Roku is currently 9.3.0 (4194-46).
For the past few weeks, I am getting normal video, but the audio is not coming through. I am thinking something has changed in how the Roku sends the audio signal that the Onkyo is not detecting what to play maybe due to the software version change. Here is what I have tried:
-Various reboots (Roku and receiver)
-Forced stereo audio on Roku menu
-Switched HDMI ports and cable on receiver to ensure it is not related to those parts. I continue to get good audio surround and video from other inputs (game consoles, etc.)
I wish I knew how else to get the Roku to talk audio like it used to do with the receiver and am open to ideas.