USBManager | USB Device Manager Show, Enable, Disable USB Device Support Windows XP, 7, 10 System | Change Data Capture library

According to the documentation the feature android.hardware.usb.host does the following:

When your Android-powered device is in USB host mode, it acts as the USB host, powers the bus, and enumerates connected USB devices. USB host mode is supported in Android 3.1 and higher.

So in other words this feature is designed to enumerate USB OTG devices like USB flash drives, webcams, or other USB client devices).

When you connect laptop and phone via USB the laptop usually becomes the USB host (master) and the phone is the client. Therefore this feature is not designed to work with such a connection and thus you are getting no device.

The only way to make it work would be to select in the USB notification menu that the Android phone should work as USB host. But as most PC are not able to act as USB client this will also not get any result.

When I plug my Phone into my PC I assumed the PC would be enumerated as either a Device or an Accessory, but it does not show up as either.

Nope. The PC is always the host, the Android enumerates on the PC as a device.

Thus you will never get the PC in UsbManager device list. This API is only used when Android is the host.

I found the reason for the problem : as stated here, Android 10 broke the UVC support during development and such devices cannot be accessed. This has been fixed on Pixels phone but not on most devices such as mine (Huawei P20 pro).

To fix the issue, it is necessary to change the target sdk version to version 27. In Android Studio, this can be done by opening the Modules settings of your project and changing the Target SDK Version in the Default Config tab. You do not need to change the Compile Sdk Version. Be aware that choosing such sdk version will prevent you from publishing your app to the android store.

I'm answering my own question here. Maybe someone else will stumble upon this. There were a couple of issues that I was not aware of:

1. The Xiaomi USB port will not continue to communicate with the sensor if it is set to USB Debugging Mode;
2. Again, even if the Xiaomi USB Debugging mode was turned off, it will not work. To make it work I had to restart the device.

The conclusion being that if you are working with Xiaomi Mi Box S make sure the hardware connection is working before you start changing anything on your code.

To make all of this work:

1. Make sure you understand how Java <-> C# communication works;
2. You will need to be a little bit familiar with Android Studio library builds;
3. Follow the instructions on the repo I posted.

You should be good to go at this point. Let me know if you need any further help.

If you going the DependencyService route, then you'll want to create a separate class that implements Interface1 and registering that as a dependency service. I don't think you can register the MainActivity as a DependencyService implementation.

One problem that you are going to hit this is mostly async code and callbacks.

You also shouldn't be newing up an Android ListView as a DependencyService call. That would be better suited as a custom renderer. As a DependencyService implementation, you would want the moj() method to return data that can be consumed by the Xamarin.Forms code. You would need more than just that method. You would need code to initialize the UsbSerialPort class, code to query the list of devices, and then invoke a callback that sends back that list, In theory anyway. I never tested that library with Forms.

As it turns out, in order for the yubikey to get data from usb, you need to have a hidden edittext on the screen to get the input event from the yubikey.