Handle keyboard keys beyond KeyCode

I am developing a windows app that needs to interface with a nonstandard keyboard with keys that include: F23, F24, audio-volume-up, and audio-volume-down (i.e. the standard volume keys). The app needs to react to all of these keys, but they are not available as inputs for Input.GetKeyDown() (which only goes up to F15, and doesn't include media keys).

Does anyone know how I could react to the press of these keys within the app?

I've noted that F23 and F24 would probably be numbered as 304 and 305 internally, but I'm not sure how that helps, given the API.

NOTE: I am using Unity 2020.2.1f1 and am primarily writing a Windows application, though it's mostly being tested over WebGL.

BUMP: Any thoughts on this? I'm wondering if I need to make a separate DLL for this. I'll be looking into it especially today as it needs to be implemented for Friday.