Yes, a naked board with firmware should still connect. It might complain defect sensors if not connected, but at least you should see it. If you use 115200 baud you should even be able to connect with arduino ide serial monitor and see the default message at startup. Hit reset button to show it again.
If you can update firmware the communication it self must work. In host make sure that protocol is ascii or autodetect, binary will not work with marlin.