hi failboat. I agree yr solution is THE mainstream solution and perfectly functioning for all networking and server related contexts WS 2016 is designed for except ONE: high end audio.
I have a highly transparent tuned stereo system consisting of tube amps, and digital preamps ( DEQX) It took my decades to build it up and of course to listen. In w10 pro I clearly can hear how snappier and transparent it is if you leave the switch out of the signal loop see https://www.computeraudiophile.com/forums/topic/30376-a-novel-way-to-massively-improve-the-sq-of-computer-audio-streaming/
Ws2016 CORE sounds very much more musical and transparent in such systems than W10.
So I stand with my original question: how to have in WS2016 two or more hardware Ethernet ports in the same computer to be in the same private sub net being also the one of the router providing internet?