* My question is, how safe is it to keep screenshots of Bitcoin/crypto transactions and useful information, on ones device?
Each of us carries a phone with us, but at any moment this device can be lost or stolen. Therefore, as a matter of prudence, you should not store any information on your phone that could be used against you. Even locking your phone with a password or fingerprint sensor may not be a panacea (If wish and have the skills, can access the phone memory).
I see the following danger when the phone falls into the wrong hands if there are "
screenshots of Bitcoin/crypto transactions and useful information". Based on transactions, it is easy to identify the contents of wallets, and the phone with a specific person, contacts and lifestyle. By comparing all this, can easily find a specific person if the wallet balance is tempting. Therefore, it is safer not to store this kind of information on your phone. What prevents your friend from saving all this on his PC if it is very important to him (For example, with an encrypted OS like Linux)?
* How do I go about letting my friend know about such a habit of taking and keeping screenshots on his device that I have observed and warn him about it, without looking like I sense bad days coming?
Tell him the 2nd paragraph from my post.