ROG Centurion base unit speaker out options

[derek\"guzlek.com]

Hi,
I have the ROG Centurion headset and base unit. I would like to connect the HDMI speaker out on the ROG centurion base unit to a soundbar that has an eARC HDMI input.

I think I have a few options
1) use an HDMI 2.0 cable from base to soundbar (tried this with various HDMI cables 1.1/1.2 and 2.0 - didn't work)
2) use HDMI on the base unit with x4 analogue 3.5mm jack and use a separate (multi-channel) analogue to digital converter with and eARC HDMI out
3) maybe order a custom cable, however, if the base unit is outputting analogue signals ill still need to convert back to a digital signal 1st


Do these options make sense? have I missed a 4th / 5th option
To double-check is the output from the HDMI speaker output on the base unit analogue or digital?

Many Thanks