Update: I just visited Dolby Audio Experience from my laptop, and it looks like they've added Dolby Atmos support to the Chromium Edge browser. I don't know when that support was added, but the video actually plays and no longer has the message directing me to use Microsoft Edge as shown in my screenshot in Post #11.
I have not verified from my PC connected to the surround receiver in the living room, but seeing as the video wouldn't even play in the Chromium Edge browser before, I think this is a good sign that this is ready to be my full time browser for every application (other than YouTube TV which requires Chrome).
I came here to update you that Edge Chromium added some Dolby stuff, but I wasn't sure if it was this or not. Good to know it now works.