Seriously add Signal, seconding your bullet point. It hits a great sweet spot of privacy and convenience for convincing people who are hesitant about new apps.
Us non profits are not safe. Case example chatgpt used to be a non profit now owned by Microsoft majorly, selling out whereโs the soul integrity none. Focus on fully European and ofc look into background of founders (did they sell out prev companies claiming principles before and to who?) and principles and track t&c changes, boards (their histories too)