Debatable. But don't touch WhatsApp either. However...

WhatsApp was based on the open source Signal protocol developed by Moxie Marlinspike. When WhatsApp sold out to Facebook, Moxie left the company in protest and started the Signal Foundation, a non-profit software company that then released the Signal app based on the same underlying protocol.

Signal has been my default messaging app for several years and I would strongly recommend it over anything else. Sound design philosophy, and strong ethos.