Sources:
[1a]
Kicksecure
Mobile Phone Security
[2a]
madaidans insecurities
Whonix Dev
[2b]
https://eprint.iacr.org/2015/1177.pdf
Luke Smith
Don't Use Telegram. Don't Use Telegram. Don't Use Telegram. Don't Use Telegram. Don't Use Telegram.
https://invidious.jing.rocks/watch?v=qBTsUVrCDAQ
[3a]
Mental Outlaw
Telegram Hands Over User Data to German Police
https://invidious.jing.rocks/watch?v=t7HZrpJ4OyQ
[3b]
Mental Outlaw
Telegram Review
https://invidious.jing.rocks/watch?v=pZEH04nJ_hE
[3c]
Android Central
Telegram reportedly gives user data to German authorities


Kicksecure
Mobile Devices Privacy and Security
Mobile devices security and data harvesting. Mobile security best practices and preventative measures against security breaches, data leaks, SIM Sw...
Messengers | Madaidan's Insecurities

Android Central
Telegram reportedly gives user data to German authorities
The messaging service allegedly complied with government data requests in some cases.