We have a Roku Streaming Stick+ we installed in August 2021. Today we can get nothing but ordinary sound, meaning no stereo or Dolby on programs that we've played before. It's not our receiver because it works fine when we use other devices, e.g., DVD player. We have the latest version of the Roku software, I believe 10.5, although I don't know when it was installed as there doesn't appear to be a version history. Our settings are set to auto-detect the best sound format (always has been set to that). We tried unseating the stick and reseating it. Didn't help.
We bought the Roku to replace our Fire TV stick. We switched back to the Fire TV stick and the sound is now good, meaning Dolby 5.1 or whatever is the best format the source comes in.
It's really annoying that you can't get phone support from Roku.
Yes, we tried the other options, and nothing changed.
As for the guide you mention, we connect with "Using optical (S/PDIF) for audio", "Connecting to an AVR or soundbar without HDMI ports", and it plays only 2-channel stereo.
BTW, we've pretty much given up on the Roku. We are using the Fire TV stick, and we get Dolby Digital 5.1 just fine. It is my opinion that either the Roku stick is defective or your software is interfering, and I think the latter is more likely. For that reason, at this point what I want is to get a refund as the product is under warranty.