The WS50 is a more basic Zebra Android device - the EMDK may run into issues with this.

The sample you refer to is a Xamarin Sample - and you may get better milage using the OEMInfo Sample:
https://techdocs.zebra.com/oeminfo/consume/  goto the bottom of htis page and find the link with the following title.

Save OEM identifiers to a file on the device | Sample app, source code ...

This will take you to a GitHub where you can get the Android Studio version of code that can function on the WS50. 

The "Device Identifiers Utility" can then be run on the WS50 (there will be a watch platform alert - you can continue to build / run past this. 
Follow the on-screen directions to allow permissions - this will setup / use the MX permissions to do this. 
Once this utility has run - look for the "/sdcard/Download/identifiers.ini" file - this .ini file will have the Serial number of the WS50.

I built / tested this app on Android Studio 2022.3.1 Patch 2 (Giraffe) connected to the WS50 RFID Version Scanner.

FYI: The sample I commented about - DOES use EMDK but in a better manner than the Xamarin does.
If you review the "ProcessProfile.java" and the "PermissionsActivity.java" in that repo; these have EMDK too.

The Xamarin App may need to be refactored to operate on Android 11.  

But this Android Studio "Device Identifiers Utility" had already refactored to Android 11 with:

GitHub indicates the app was updated from V1.5 to V1.6  in the Build Gradle file.
The "AndroidManifest.xml" was adjusted to clean up line 16 to have simply:  

<package android:name'com.symbol.emdk.emdkservice"  />  and removing the :

<provider android:authorities="oem_info"  />  on the same line 16 in the <queries> tags.