It would never have been on Google Play or App Store if the three letter agencies didn’t have some sort of control over it. Sadly there probably won’t be anything that’s widely accepted my most people and is secure from eavesdropping. I find it hard enough to get people to switch to Signal. Making a switch again to something like Threema probably won’t happen.

Snowden suggested it, obvious honey pot

Even if it’s fully end to end encrypted, there’s this too:

https://youtu.be/IWMZ17Iyu3o

This guy has a great channel dedicated to privacy. I recommend checking out some of his videos if interested.