Interesting that people in sensitive positions would use foreign made smartphones. Surely they are Russian companies that manufacture at least low end Android phones?
Looked this up and there is indeed a Russian company called Ayya, making smartphones with a switch to disable the microphone. It'll also be changing from Android to a domestically made OS, it seems. https://www.indiatimes.com/technology/news/russia-ayya-t1-sm...
If you are truly concerned for your life, especially in authoritarian regimes, don't carry a phone.