In any case, try the following basic suggestions: Make sure to set HDMI as the default output connection for both video and audio. Try booting PC with the HDMI cable connected to a TV that is on.
It’s also true, of course, that HDMI cables were designed with the best of intentions: to provide a single-cable digital video and audio solution. Nonetheless, it’s clear that plenty of HDMI nonsense ...
However, if you want HDMI passthrough you still won't get that ... The Arc was no stranger to three-dimensional sound output, with virtual Dolby Atmos surround achieved in a 5.0.2 output ...