"ArgumentException: GameObject to save Prefab from must be a Prefab root" thrown when running Built-in to URP > PPv2 Converter

How to reproduce:
1. Open the attached project "corgi-dr-noob.zip"
2. Open Window>Rendering>Render Pipeline Converter
3. Select "Built-in to URP" in the dropdown menu
4. Select "Post-Processing Stack v2 Converter" at the bottom of the Render Pipeline Converter window
5. Click Initialize Converters
6. Click Convert Assets

Expected results: No errors thrown in the Console window
Actual results: "ArgumentException: GameObject to save Prefab from must be a Prefab root" error thrown in the Console window

Reproducible with: 2021.3.6f1, 2022.1.9f1, 2022.2.0a19, 2023.1.0a3
Could not test with: 2020.3.37f1 (compilation errors in the Console window)

Reproducible on: Windows 10