You can also do real Ethernet with a teensy: https://www.pjrc.com/teensy/td_libs_Ethernet.html

Thanks for that, I like the compactness of the Teensy solution. If we're going with shields it's probably worth mentioning that the Arduino also has one:

https://www.arduino.cc/en/Main/ArduinoEthernetShield

Interesting concept, even if a bit too hacky, thanks for the link! (and probably possible with all kinds of fast-ish systems with DMA)