For Dolby Digital, this is the first HDMI adapter to support 2.1, for 4K/120: https://www.amazon.com/dp/B0B73P5VX4

A more affordable option is an analog-to-digital converter, but it will only support stereo: https://www.amazon.com/dp/B07W5GNZX5

Your confusion is understandable; mini-TOSLINK is so similar in shape to 3.5mm aux, that some laptops actually have a port that combines the two: 3.5mm aux with an optical LED inside.

This is what you need: https://www.amazon.com/dp/B07W5GNZX5

The monitor’s headphone port (and converter’s input) is stereo only, so for surround sound, use Dolby Atmos for Headphones (included with the Gen 4 MixAmp Pro TR for Xbox), and set the MixAmp to Star.

Also, Astro Command Center can run on Xbox.

Analog to digital: https://www.amazon.com/dp/B07W5GNZX5

It only supports stereo, but so does Dolby Atmos for Headphones, which is included with the A50 Gen 4 for Xbox.