🙂That's funny, I was doing exactly the same thing as you yesterday! I'm not sure YouTube supports 9.1.4 - I found lots of videos claiming they were for testing Dolby Atmos but they were only 5.1 (showing in the YouTube video setting). Some were even just stereo. On my HW-Q930D if you hit the i button on the soundbar remote a couple of times it shows you what the sound format its playing on the soundbar display.
I think we'd either have to use a blu-ray player, xbox or stream from Disney+ Premium, Netflix Premium, AppleTV+ or Amazon Prime etc.
I haven't actually experienced Dolby Atmos yet (at least I don't think I have!).
