LG C9 GSYNC means no surround sound

I'm one sad panda.

In order to get VRR you need to connect the graphics card directly to the C9 which makes perfect sense. But then to get surround sound from games to an AVR you need multichannel PCM over HDMI ARC which LG does not support!

Also tried an optical cable directly from the PC to AVR but that also doesn't work because optical only supports 2 channel PCM and on the fly DTS and Dolby encoding is broken on Windows 10.

Incredibly frustrating! Any ideas on how to work around this mess?