Without question,
HDMI i2s
Sadly not speaking of I2S (my Master 11 is RJ45) and even then it's depending on the converter (USB>I2S) but yes, I have the HDMI input on my Master 7.
That said, I have some options for S/PDIF input/output, RCA, BNC or TOSLINK from a Wyred4Sound Remedy Reclocker. Ordering a BNC S/PDIF cable from Blue Jeans Cable and wondering about why the BNC input is rated lower speedwise than the RCA?
yea, you can install the hdmi i2s module. it's plug and play. 5-10min process.
but the DDC is critical as you say. But since you have RJ45, maybe the breeze would work. I have not used RJ45 with it before....but I think it should work
otherwise, I'm using a DIU8 from audio-gd with ndk upgraded crystals. the crystek 957's were good too, but ndk surely is the most ideal setup.
i2s is by far the lowest latency, also cleanest sound quality.
and BNC uses a diff IC than the digital RCA hence the difference of 96k vs 192k.
I have some great digital RCA's that come close to performance of i2s, yet latency isn't as great. I have a graphene extreme from cerious technologies and also MSA heretic carbon fiber digital coax. Both sound pretty darn good. And you can use BNC if you want, but will always be limted to 96k. It does sound great through either imho.
I still prefer i2s as it's a step up without question.
I have a heavily modded gustard u12 for sale (cheap) that is modded for audio-gd hdmi i2s. AckoDac voltage regulator of 1.6uV - also converted to linear power input (gutted a/c mains and transformer) (now 7V dc input) and also has crystek 957's! sounds damn good for i2s. I don't use it anymore since I got the DIU8, yet its definitely better than the amanero combo. One down side is the coax doesn't work on the u12.