I had a similar issue. I use one of these now

https://www.amazon.com/HDMI-Audio-Extractor-Splitter-Converter/dp/B07DFDQ6HG

What you need is a HDMI Audio Extractor. So it should have 2 HDMI slots and an optical port as well. With that, you'll be able to make full use of the G6 and the new game and party chat mix function on the PS4.

https://www.amazon.com/dp/B07DFDQ6HG/ref=cm_sw_r_cp_awdb_imm_KDKVYQKQ7371ARHHJHWP

This is a good one if it fits into your budget but my advice to you from my experience is, get a good one rather than a cheap one and end up having to buy replacement units when they fail you. Hope this helps! ☺️

How it works is : You'll need one HDMI cable from your monitor/tv to the HDMI OUT port, one HDMI cable from the ps4 to the HDMI IN port and the optical cable in the SPDIF port to the G6.