Telegram stores all data on own servers.
Just try the following trick:
- in a private Browser window open web.telegram.org
- enter your phone number, receive the code
- turn on flight mode on your phone
- now enter the identification code in your browser
- access your whole chat history while your smartphone can definitely not act as a source
Even WhatsApp is better in this regard.
Article in German: https://www.heise.de/hintergrund/Telegram-Chat-der-sichere-D...