Electric Bass with RJ45 Digital Output I'm working on a project bass guitar with individual outputs per string using Nu pickups from Cycfi Research: https://www.cycfi.com/
The common sense approach is to simply take their circular connector and use this to interface, but I'd like to know how realistically could I use a multichannel ADC/MCU to convert the 4 (or more with scalability accounting for 5 strings or two pickups) outputs serially to an RJ45 in real-time?  The goal would be to preserve each individual output to process digitally in a box or use a DAC to split the channels back out to process with analog pedals (for example).
This is a question of &quot;could&quot; not &quot;should,&quot; and it comes from a place of learning, tinkering, desire to use a more commonly available cable for lower cost (the circular is a good deal for its quality, but it's $84 and not common), and the ability to send power all in one cable.  Development time, headache, and cost of electronics inside or outside the guitar are not a factor, this is a hypothetical since I just don't have experience working with multichannel ADCs or ethernet and I'd like to use this as an alternative project to learn from.
I don't mind if this is wrong, I'd just like to understand if this is a rabbit hole or the elusive unobtainium.  Thanks in advance!
I'd just like to understand if this is a rabbit hole or the elusive unobtainium.

A little bit of both. Ethernet is really NOT a great choice for real time audio. You would need a fairly beefy processor that can handle a network stack (TCP or UDP). Getting the latency down to something that's playable is extremely challenging.
Even if you get it on Ethernet, where would it go ? There some multi-channel network formats but these tend to be in the PRO space  and expensive.
If you just care about the connector, you can certainly run I2S or TDM through an RJ45 + Ethernet cable. That works quite well (and I've actually managed to incorporate this into a commercial product). Again, you would need some type of receiver that's matched to your transmitter.