Reproduction steps:
1. Open project in CloudAnchorsTest.zip (3.2 MB)
2. Go File - Build Settings
3. Switch platform to iOS
4. Enable Development Build and Script Debugging
5. Build for iOS

Expected result: Build completes successfully
Actual result: Build fails

Reproducible with: 2020.3.1f1, 2021.1.0f1, 2021.2.0a10
Not reproducible with 2019.4.22f1
Could not test with: 2018.4.33f1, because could not resolve package errors (note 4)

Notes:
1. The project uses the ARCore package imported manually via path local to the project (seen in manifest.json)
2. Not reproducible with a new project
3. If packages need to be reset, you will have to include ""com.google.ar.core.arfoundation.extensions": "file:../../arcore-unity-extensions" in manifest.json
4. I could not test if this is a regression because on some versions I could not resolve the package errors (Usually earlier version of the streams). I left some info on edits