As a former Telegram user, I thought this reminder was pertinent (and is partially why I left the platform). The following is from Signal founder Moxie Marlinspike, on Twitter a month ago:

Telegram is the most popular messenger in urban Ukraine. After a decade of misleading marketing and press, most ppl there believe it’s an “encrypted app”.

The reality is the opposite — TG is by default a cloud database w/ a plaintext copy of every msg everyone has ever sent/recvd.

Every msg, photo, video, doc sent/received for the past 10 yrs; all contacts, group memberships, etc are all available to anyone w/ access to that DB.