Apple is disabling and tracking some looted iPhones
https://www.marketwatch.com/story/apple-is-reportedly-disabling-and-tracking-looted-iphones-2020-06-03
Propietary
The Quest to Build a Truly Free Version of Android | WIRED
“…if you really care about security, you should avoid using a phone at all.” http://www.wired.com/2013/10/replicant/