Problem with ARSession.CheckAvailability()

Hi,

I'm trying to check for AR availability for an app that should use AR Foundation if available. I have this code:

 using UnityEngine.XR.ARFoundation;
 
 // ...
 
     IEnumerator CheckSupport()
     {
         // UI feedback
 
         yield return ARSession.CheckAvailability();
 
         // execution never reaches here on unsupported device
 
         if (ARSession.state == ARSessionState.NeedsInstall)
         {
             // more UI feedback
 
             yield return ARSession.Install();
         }
 
         // even more UI feedback
     }

I start this coroutine at the end of Start() in start screen so that I later know which alternate scenes I should load. I'm using Unity 2019.2.3 with AR Foundation 2.1.3, AR Subsystems 2.1.0 and ARCore XR Plugin 2.1.1 (besides other stuff, but those are the relevant packages). I configured ARCore as optional and have API level 16 (Android 4.1) as the minimum API level.

On a Nokia 6.1, which supports ARCore, this works as expected, including installation of the necessary components if I removed them. On a Nexus 5 with stock Android 6.0.1 installed (no ARCore support), CheckAvailability() never returns and ARSession.state remains on ARSessionState.None. I don't have other devices to test.

What am I doing wrong and how can I fix this? Or how can I work around this if the fault lies with Unity or AR Foundation? My only idea currently is to implement a timeout and assume "unavailable" if that triggers, but that sounds risky (no idea how long checks can take on some supported devices) and I would still have a rogue coroutine.