I am a firm believer that there are many privacy techniques you should focus on before encrypted messaging because they will offer you much more “bang for your buck,” things like good passwords, two-factor authentication, and even encrypted email. That said, I still believe that encrypted messaging is a critical part of a well-rounded privacy and security strategy. While the vast majority of our day-to-day conversations may be benign, it can still offer a lot of insight into who we are as people – our routines, likes, and personal thoughts. This information – mundane or not – is worth protecting.
If the app implements their own notification system and doesn’t rely on GCM then Google isn’t able to log them as far as I know.
I can throw a few examples:
- SimpleX
- Threema Libre
- Briar (afaik)
- Conversations (XMPP client)
- FluffyChat (matrix client), probably some others too
- Telegram FOSS (Telegram fork), Mercurygram (Telegram FOSS fork)
- Molly (Signal fork)
- Session F-Droid (Session fork)
So, the answer is — almost every of them.
But not Signal? I use Signal but I’m not sure I can get my chat groups to use something else.