AR Foundation 3.1 Samples: "Simple AR" scene not working

Hi all!
I have built the "Simple AR" scene of the samples on GitHub with:

• AR Foundation 3.1
• ARKit XR Plugin 3.1
• Unity 2019.3.5f1
• Universal Render Pipeline

When I run it on my iPad Pro (2nd gen) with latest iOS 13, I can see the AR Camera Background (i.e. the camera image), but it seems it cannot detect any surfaces, since I can't spawn cubes by tapping on screen.

I can see yellow dots, representing Cloud Points, so that seems to be working. Also, I'm not sure what does it represent, but after some time since I launched the app, I start to see poligons at the edges of the screen. Maybe they should represent detected surfaces? But they are "sticked" to the screen, they don't seem to be in AR session space. But I have simply built the "Simple AR" scene as is, without modifying it.

Any tips? Thank you in advance for your answer!