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

[sisu]

My setup:

FireTV Cube -> LG C3 -> HDMI ARC (not eARC) -> Pioneer A/V Receiver

- When playing contents with DTS -> Receiver receives and process the 5.1 signal correctly
- When playing contents with AAC5.1/7.1 -> Receiver just sees 2.0

Is there a setting that I need to toggle through the TV or FireTv or Jellyfin that would sends the AAC5.1/7.1 signal to the Receiver correctly?

OR

Is it the receiver that's not playing nice?