Let’s break down what this device actually is and how to fix it in under two minutes. Contrary to what the generic name suggests, this isn't a legacy COM port for a mouse or external modem. On the ThinkPad T510, this device is the Intel Active Management Technology (AMT) / Management Engine Interface.
Tech Retrospective Date: October 26, 2023
You didn’t miss a cable. Your motherboard isn’t dying. You’ve simply run into a classic Intel Management Engine (MEI) driver quirk.