arcoresdk+unity urp let background blue

[ar4ds]

VERSIONS USED

• Unity: 2020.3.13f1
• ARCore SDK for Unity: arcore-unity-sdk-1.25.0.unitypackage
• Device manufacturer, model, and O/S: OPPO RENO
• Google Play Services for AR (ARCore): 1.25.2114600063

STEPS TO REPRODUCE THE ISSUE

1. get arcore-sdk from github
2. following urp setting guide
3. when app's running, the background only show camera's solid color

WORKAROUNDS (IF ANY)

when i install 'ARCore XR Plugin' from Unity 'Package Manager', the background works,but api is not enough for me.
so i can only use standard render pipeline now

can you give me some advice, thanks!