For my game I’m using the ARCamera to let the player make a selfie. For that I have a screenshot code but I also used ScreenCapture.CaptureScreenshot(“test.png”). It always results in a a black render texture of my gps map. For the gps map I also use a camera with a render texture. If I use the normal camera it seems to not generate the problem!!!
ScreenCapture is not an XR API. You might get more traction with this question on the general forum: Industries - News & General Discussion - Unity Discussions or possibly the iOS forum: Unity Engine - Unity Discussions or Android: Unity Engine - Unity Discussions
But the problem lies into the XR section.
You are welcome to file a bug: Unity QA: Building quality with passion
The XR team does not own this code, and we will not be the ones to fix it. But if you file a bug, our QA team can help you reach the right team.