-Background: MSFT reported to XR team that with new action-based Tracked pose driver, Camera becomes head-locked when 2D overlay app is opened on Holoens2. This regression started happening since Input system 1.1.x and head tracking works fine in 1.0.2 package. This is a huge blocker for their MRTK v3 adoption.

-Discussion: from the discussion with input team, 1.1.x introduced completely reworked focus handling behavior and introduced the RunInBackground rules, which caused the regression. Slack thread: https://unity.slack.com/archives/C09Q7LYP9/p1642567199067700. Desktop/UWP platform can work around this issue by enabling Run In Background in player setting for short-team fix. But for Android platform. it is not possible to work around it since no RunInBackground option available. I also tried to force backgroundBehavior = ignoreFocus in script on Android, still not working.

-Requests:
For short term fix: Head tracking pose/input data should keep running regardless of the background state.
For long term: we need a clear way for the input system to know the differences between visibility lost on the headset or input lost, which are two discreet stats in OpenXR. With Visibility off, all input can be ceased, but if Visibility is on, the headset must keep tracking.