FireTv Jellyfin passing AAC5.1 through HDMI ARC as 2.0?

[Plonker]

I have the same issue with AAC 5.1 playing back as Dolby Digital 2.0 (according to Sonos) in my setup. I can play Atmos, DTS and Dolby Digital 5.1 without issue, but anything that is encoded in AAC 5.1 plays back in stereo only. I've checked that "Audio Output" is set to "Direct" and as I've mentioned, it 100% works with other standards. My setup is Jellyfin 10.10.1 > Sony Bravia UR3 (Android 10) > Sonos Arc (via eARC HDMI). Anyone experiencing similar? Don't really know where to start with getting to the bottom of this.

Edit: Just realised this post is 2 years old, I'll start a new one! Soz.