iPhone location tracking
https://www.theverge.com/22676312/ios-iphone-apple-location-tracking-turn-off-on
"To check whether your phone is still collecting location data, go down to
the very bottom of the 'System Services' screen and toggle the switch on for
'Status Bar Icon.' This will display an arrow at the top of your screen when
an app on your phone is accessing your location.
If you have a phone designed with Apple's U1 chip − such as an iPhone 11 or
later − and have disabled location services for specific apps, you may find
that you still sometimes see the arrow. According to Apple, this is because
these models use ultra wideband technology, which Apple says is regulated,
so the phones use location services to determine if they're in an area where
ultra wideband use is restricted.
The iPhone requests location data when location preferences are set on an
app-per-app basis, so switching off location services for your phone overall
will stop these location requests since your phone won't be able to collect
any location data."