I’ve seen a lot of posts about this on the forum but they all seem to be resolved by changing the TV settings but I have tried all that and I’m stumped!

I tried my Apple TV 4K (2022) and also a Google Chromecast with TV connected to the projector HDMI 1, Sonos Beam gen2 connected to HDMI 2 (eARC).

If I set the projector audio to "Bitstream", I only get PCM 2.0 coming from the Sonos.

The projector only has two audio output options, Bitstream and PCM. Viewsonic told me that PCM is for output via the projector’s internal speaker. Nevertheless I tried the PCM option and nothing at all comes out of the Beam so that tracks.

Now when I connect either of these streaming devices to my LG TV and then Sonos on the TV's eARC, with the TV set to “Pass Through” the Sonos plays Atmos correctly.

Also with the Chromecast there's an option to detect all the available formats supported by the audio device, and through the TV eARC I can see Atmos listed, but through the projector eARC the Chromecast can't detect anything.

Viewsonic claims on their side that the projector can correctly pass digital audio.

There’s just not a lot of levers to pull on the Sonos or the projector so I’m totally stumped.
Appreciate your time reading this