Surprisingly Telegram awfully good on that list
Edit: I forgot to add that I found something little of about that report where Signal hash to phone numbers are absent " Which clearly signal store it"! And on Threema FBI still includ it even though it’s optional and 99℅ of the user will not put their number.
So Apple is the worst privacy, surprise, surprise! And Telegram is the best (of the worst, in US), but how knows what KGB can see :D
except iOS warns you that enabling icloud backup for whatsapp is a terrible idea. whatsapp is really just terrible all around, because you don’t know if the user you’re talking to does have backups enabled. it’s like relying on PGP, you have no idea if it’s being used on the other end, so, might as well not treat email as something secure.
If your backups are accessible to others then you have no privacy no matter what tools you use, it is the ultimate back door. Same as running “scanners” client side.
I’ve been using Session lately. Not sure how it stands up on the technical merits.