I recently imported Google ARCore into my Unity project and when doing so this error appears:

GUID [bd091fc8013c942f586c1672b8ee2b27] for asset ‘Packages/com.unity.xr.arcore/Runtime/Android/unityandroidpermissions.aar’ conflicts with:
‘Assets/GoogleARCore/SDK/Plugins/unityandroidpermissions.aar’ (current owner)

We can’t assign a new GUID because the asset is in an immutable folder. The asset will be ignored.

My Unity version is 2019.4.12f1 and the ARCore version is 1.20.0

Any thoughts?

Same problem, I fixed mine by uninstalling ARCore XR Plugin using the package manager, then restart Unity. You can leave AR Foundation, ARKit XR Plugin installed.