Is there a way to monitor the signals an HID (Human Interface) device sends to the OS?
NSEvent

To monitor input events sent to macOS from Human Interface Devices (HID), look at NSEvent's addGlobalMonitorForEventsMatchingMask:handler:. This is the method used to associate scripts and tasks to hotkeys by third party macOS tools.

You will likely need to write in Objective-C or Swift and codesign the resulting binary. I expect you will also need to grant the binary additional access rights at runtime – probably in the Accessibility panel of System Preferences > Security &amp; Privacy.

A search on GitHub will provide a few sample projects using this method.