Enabling “Sample Loader One Custom” in XR Plug-in Management throws “Unable to add package” error in the Console window

Steps to reproduce:
1. Create new Unity project
2. Open Package Manager window
3. Find and install XR Plugin Management package
4. Open Project Settings window
5. Find and select “XR Plug-in Management”tab
6. In XR Plug-in Management > Plug-in Providers check “Sample Loader One Custom”
7. Observe the Console windo

Actual results: "XR Plug-in Management error. Failure reason: Error Message: Unable to add package” error is thrown in the Console

Expected results: No errors should be thrown in the Console window

Reproducible with versions: 4.5.3 (6000.3.0b7)
Can’t test with versions:  6000.2.9f1 and lower (“Sample Loader One Custom” is not available in Plug-in Providers list)

Tested on (OS): Windows 11