> Android devices can advertise in the background but they can't scan reliably, they can do this for a short period of time enforced by the Android time limits

> Android devices can advertise in the background but they can't scan reliably, they can do this for a short period of time enforced by the Android time limits on apps running in the background and possibly manufacturer specific power savings measures. Since Android 8.0 there are no time limits for background scanning if you're calling startScan() with a PendingIntent. It's not 100% reliable, particularly on devices which aren't on stock Android as you mention, but it works reasonably well.