I created a new project with your code and tested it on the physical device with Android 14.0. But the app will crash when I clicked the button. I found the cause is the permission after I checked the nuget package github repo:
You can check the part about the Android permission:
Android 12 and above may require one or more of the following additional runtime permissions, depending on which features of the library you are using (see the android Bluetooth permissions documentation)
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" /><uses-permission android:name="android.permission.BLUETOOTH_CONNECT" /><uses-permission android:name="android.permission.BLUETOOTH_ADVERTISE" />The adapter.deviceDiscovered was fired after I added the permission above into the AndroidManifest.xml.