You might be interested in Peergos [0][1] which is E2EE, fully open source (including the server), and self hostable. We've been audited by Cure53 and Radically

You might be interested in Peergos [0][1] which is E2EE, fully open source (including the server), and self hostable. We've been audited by Cure53 and Radically Open Security. [0] https://peergos.org https://peergos.org [1] https://github.com/peergos/peergos https://github.com/peergos/peergos