tl;dr: Chatto, a self-hostable group chat app positioned as a Slack/Discord/Teams alternative, is now open source and available via Homebrew or binaries for Linux, macOS, and Windows. It features encrypted-at-rest data with per-user keys, built-in E2EE voice/video/screen-sharing, and a single-server-per-community model (no federation). A paid hosting option, Chatto Cloud, is launching in beta on European infrastructure; the project is at v0.4 and expected to reach 1.0 in 6–12 months.