What we need is a SBC with two ethernet ports.
New version in the works based on the same RK3399 chip as the Tinkerboard from the article.
NanoPi R4S https://www.cnx-software.com/2020/11/12/nanopi-r4s-headless-...
Thank you. I will add this to my list of candidate devices for a “network slug”.[1]
Haven't had a chance to run my R2S in production yet but it can do >930Mb/s in iperf3 on both ports, so that's a start.
You can even get N-BaseT USB3 adapters these days, and USB3 has the bandwidth. You may quibble about connecting Ethernet over USB3, but it works quite well in my experience.