Doze broadcasts aren't received on Nokia 3.1
A log from the Snooze app running on the Nokia 3.1 doesn't show any broadcasts indicating that the device entered or left doze mode (device idle mode), unlike ten other devices that were tested. On all devices, the app was exempt from doze, running a foreground service and holding a wake lock.
If Briar likewise doesn't receive doze broadcasts on this device then it may fail to detect that its doze exemption has been removed. We only check the exemption status if a doze broadcast has been received since the last check.
I've asked @earthlingIB to run another test on this device without the doze exemption, to see whether it's the exemption that prevents the broadcasts from being received. If that's the case then we can close this ticket, as Briar will still be able to detect if its exemption has been removed.