The RP2040 can be convinced to bit-bang Ethernet (yes even 100Mb/s) with only a transceiver. Part of the trick is to modify the common PHY + MagJack breakout boards to let the RP2040 generate the clock signal so that the signals are in sync and you don't have to oversample the RMII.

Just 10Mb/s can be done even dirtier. I'm still waiting for someone to combine an RP2040 with DVI/HDMI video output and Ethernet into a "modern" glass terminal (just telnet, SSH is probably asking too much).