Best way to get MAC address from offline devices?

I have a warehouse full of equipment and I need to get each device's MAC address. Without putting each device on the network, what's the best way to get their MAC addresses? Is there an Android or iOS app I could use with a USB-C to ethernet adapter to show it? Windows/Mac/Linux laptop and a script or program? It's several hundred devices, so ideally I could plug in power and ethernet, get the MAC address, and move to the next one.