Steps to reproduce:
1) Download the attached project and open it in Unity
2) Open “Repro” scene
3) Open the Package Manager and install the “Universal RP” package
4) Open Render Pipeline Converter: Window >> Render Pipeline Converter
5) Make sure the converting mode is “Built-in to URP”
6) Select all the converters and click on the “Initialize Converters” button
7) Click on the “Convert Assets” button

Expected result: Built-in Read-only materials are converted to URP Read_only materials
{}Actual result{}: Built-in Read-only materials are not converted properly and rendered in magenta

Reproduced with: 2022.2.0a5, 2022.3.26f1, 2023.2.19f1, 6000.0.0b16
Not reproduced with: 2021.3.37f1, 2022.2.0a4

Tested with:
MacBook Pro (16-inch, 2021), CPU: Apple M1 Max, Memory: 64 GB, macOS: Monterey 12.6 (21G115)