What is one-bit audio?

In plain language

Direct Stream Digital represents audio as a very fast stream of single bits rather than multi-bit samples. It is the format behind SACD and some high-resolution downloads, and it travels over HDMI in its own way.

Why it matters in your setup

Only if you play SACDs or DSD files. When you do, it matters completely: a chain that does not advertise one-bit audio means the player converts to PCM or refuses, and the point of the format is lost.

Because it is niche, it is also the capability most likely to be dropped by a device in the middle that was never tested with it.

What the DR HDMI 8K does with it

ONE BIT is one of the DR HDMI 8K's audio flags, with its own enable setting and sample rate, and DSD and DST appear in its supported audio formats. For an SACD player in a chain with a receiver in between, that flag is the thing to check first.