Chadder - Encrypted messaging app
Encrypto - Encrypto lets you encrypt files before sending them to friends or coworkers.
GrapheneOS - GrapheneOS is an open source privacy and security focused mobile OS with Android app compatibility.
MagicPad - Free, simple, and private, offline text encryption suite.
Earlynote - A time-travelling messaging app
Tresorit - Encrypted cloud storage for your confidential files. Using Tresorit, files are encrypted before being uploaded to the cloud. Start encrypting files for free.