To be fair, not everyone knows about the chat apps. And not everyone knows signal is backdoored.
I'm not saying it to be mean. I'm telling Nostr friends SII they can be informed.
Discussion
None are really secure. The most secure encryption and best designed application can be defeated by a screen shot
Well that is really a whole other thing.
0xChat and SimpleX are both fully e2e. So they are secure. And as far as we know, not back doored.
If your friends are screenshotting sensitive information then you have a friend problem not an app problem. If screenshits are being used as an argument for Signal, which is back doored... It isn't.
You can set the chats in both 0xChat and SimpleX auto delete after X time. Not perfect but at least something.