Dedicated Ethernet port for that SBC; connect over SSH the usual way. (Our code doesn't need to worry about authentication nor encryption).
-Serial ports. Lots and lots of serial ports. For a standard server, just wire up to the serial port for interfacing. For the half-broken coreboot on the D16s, wire serial port RX to the D16's TX (for early boot log) but port TX to the RX pin of a serial->USB HID adaptor (so we pretend to be a keyboard).
+Serial ports. Lots and lots of serial ports.
-To manage an entire fleet by the same board, external USB->serial multiplexing adaptors can be used, so we can have e.g. 5 serial ports (5 servers) on the same port .
+To manage an entire fleet by the same board, external USB->serial multiplexing adaptors can be used, so we can have e.g. 5 serial ports (5 servers) on the same port.
For power output and similar tasks, connect like a switch using the board GPIO. For a small number of servers, we can wire up directly to the board GPIO; for a larger number, I imagine USB->GPIO adaptors exist.