Actually, I've figured it out. I had the I2C lines running next to the 50MHz clock, and that induced enough 50MHz "noise" onto the I2C lines, (about 1v peak to peak in amplitude), to make the KSZ8863 Ethernet switch unable to differentiate between the actual 1s and 0s. Next revision will be a 4 ...

I think an ESP32 can definitely handle this job.

I'm using an ESP32-WROVER-E module with the KSZ8863 chip to give my ESP32 an Ethernet interface while also allowing my device to be daisy-chained to other devices. At first, I was testing the KSZ8863 with this breadboard mess.

https://preview.redd.it/having-trouble-with-esp-idf-ksz8863-simple ...