Does the Nucleus HDMI output an I2S signal?

I’m interested in using this with my PS Audio dac.

No. I2S is not supported by HDMI.

What PS and some others have done is to appropriate the HDMI connector for their proprietary I2S connections. Decidedly off-label use.

Thanks KAL.
Anyone know if there is a limit to the hard drive size that can be installed internally.

no limit, but the size must be 2.5" / 9.5mm or smaller. that pretty much limits you to 2tb in spinning drives and 4tb in SSDs for now.

I2S is a synchronous transmission; the DAC will lock to the source clock; thereby generates high amount of jitter. They are designed for point to point short connection in the PCB.

Asynchronous like SPDIF and USB are more preferred way to send data to a DAC due to virtually absent of jitter.

Anyone have a suggestion for a hard drive that is very quiet?

any SSD will be silent

But SSD’s are very expensive

Unsure how much space you need, but 2TB SSDs in 2.5" form factor are pretty affordable at less than $300 nowadays.