How would I determine an issue between motherboard, and I/O board?

My index video and audio have not worked since ~2021. No trauma or water damage to the system. First the audio gave out, then a few weeks later the display gave out. Diagnosing the issue, steam vr recognizes the device, tracks, and even has the facial distance sensor working. lights and indicators turn red after it realizes it can't find a display after ~5 tries of looking for one.

A few weeks ago, I ordered a new trident cable and tried it, same issue. I've checked drivers, different computers. Checked cable connections. The works.

This has led me to believe it may be an IO port issue, because I can't understand everything else working if it was a motherboard issue. Hopefully it is one or the other, because it'd be a shame if I couldn't figure out the root issue. What are your thoughts?