It is also the app that is used by BLM and Antifa as a form of communication. I do not understand this because it is stupidity to use a form of communication that your enemy is aware of and monitors. These people are not smart.

According to E. Snowden Signal is secured even if used by Patriots. It can be understood since there is no central server (like Whatsapp of FB messenger) for saving text. I use signal and copies of my text are only on my devices. You can even set a timer and messages will disappear thereafter (like Mission Impossible :-). However if you want better confidentiality you can used apps like encrypto to cipher any kind of files with a shared Key.