It is odd that you can't force stereo though. I'd guess that most people use the builtin TV speakers, then soundbars (which are barely surround at all despite

It is odd that you can't force stereo though. I'd guess that most people use the builtin TV speakers, then soundbars (which are barely surround at all despite the marketing claims) second, and proper surround a very distant third. So it's surprising that they don't cater to what is the most common output format. I guess the app just works on whatever the PS4 has set as max capability on startup, which unfortunately for you is 5.1 or 7.1 because it's going out via HDMI. Pity ps4 slim doesn't have spdif out, in that case you could have used that and set to PCM output which would force stereo. I just read that ps4 supports usb soundcards, maybe you could buy a cheap stereo soundcard and use that to force stereo. Don't know though because all the cheap ones that I've seen tout virtual surround "3D audio" as a feature, so who knows if that would work. All this whizz-bang technology and you can't just set it to default to use only the number of speakers that you actually have...