I downloaded this YouTube video in both MKV and MP4 formats using 4K Video Downloader and MediaInfo confirms both contain 6-channel AAC LC audio.

The downloaded files, when played in PotPlayer v1.7.21126 (released in February 2020), definitely contain separate channels. It worked perfectly as intended.

However, when I play the video in YouTube(highest quality available; 1080p) in Google Chrome v80 (released in February 2020), I only get stereo (or fake surround - the rear channels play primarily through the front speakers).

Same issue in Internet Explorer 11.719.18362 and Microsoft Edge 44.18362.449.

Windows is set up correctly as, as I said, PotPlayer played the individual channels in the downloaded video file fine and all games work in surround as they should.

Any ideas?