How to troubleshoot/resolve "Signal strength query returned error" logs that are appearing in Xcode 10.1/iOS 12.1?
It seems to be a side-effect of calling [CTTelephonyNetworkInfo new]; under newer versions of iOS and can be safely ignored, I think. I'm not sure there's anything app developers can do to fix this, it appears to be a side-effect that signalStrength inside CTTelephonyNetworkInfo is hidden from public apps in recent versions of iOS (9+). This is nothing new, but it's noisier about the permissions error here under iOS 12.1 (maybe other versions?).
CTTelephonyNetworkInfo appears to be a hastily-revised API, for public use at least: For example, it had bugs in v12 when returning carrier info that was fixed in v12.1. why do serviceSubscriberCellularProviders return nil? (in iOS 12)
I'm also reminded of the extraneous permissions errors that appear frequently in macOS console logs - https://eclecticlight.co/2016/09/23/sierras-console-promising-but-incomplete/ - or the Xcode 8 bug where in an early beta the Simulator was extremely noisy. Sometimes the internal chatter slips out to an external release, and there's not much anyone outside Apple can do about it...