Mac Studio output Dolby Digital 5.1, paired with Sonos Soundbars

Hi,

Anyone know how to reliably connect the Mac Studio to a decent soundbar ?

My use case is to watch movies via the Mac Studio, ideally to a Sonos soundbar.

Looking for

i) optical (for a minimum of Dolby Digital)

Or

ii) HDMI for Dolby Atmos.

The screen is an LG ultra wide, which does not HDMI ARC, so that presents some challenges in terms of Dolby Atmos.

I have tried a Realtek USB-C to Optical converter which does seem to present an output of 5.1 to my Sonos soundbar, BUT, in the MacOS midi utility it only shows up as 2 channel output, not 5.1 (however the Sonos app shows a 5.1 signal)

Is there a way to use the Mac Studio HDMI to connect to HDMI Arc on the soundbar?

Lots of questions there, any help appreciated.