Does the Series X|S support DD and DTS? Because if not, optical doesn't have the required bandwidth to transmit 5.1 PCM, maybe that was a deciding factor in not bothering to put a legacy connection on it?
Plug your headphones in to your controller.
Headphones into controller is literally awful. There's so much compression it sounds like ****, all the time.
The point is that, due to the loss of a $2 optical, we now need to spend $50+ either in the form of an audio extractor (does VRR still work if you use one?), or an expensive AV receiver just to convert HDMI to optical out/line out/headphone out, depending on how much you spend on the AV receiver, or whether you want to use an existing DAC/amp, etc.
That $2 saving has screwed people who want to use their existing headphones and DAC/amp setup. There really was no need for it.
And once again, the headphone out on the controller is awful. Not just the compression, but it won't drive many headphones anyway.
e: HDMI audio extractor does NOT work with VRR, according to Google. So that plan is a wash anyhow.