Cannot play 5.1 content on new Windows HTPC
I have a new Windows PC with an 8th Gen Intel i3 and a motherboard that says it supports up to 7.1 audio. When plugging the machine into either my TV or my Vizio soundbar, Windows will only show stero as an option and no matter what I choose in plex it will downmix to stero. What do I do to enable 5.1 on Windows? I've updated the BIOS and graphics drivers on the PC and all other device's firmwares are up to date.