• matrix-synapse (Closed registration, DM me for invite) (private decentralized messenger with military-grade encryption). Also includes mautrix-telegram bridge
• jitsi meet (Closed registration, DM me for invite) (VoIP and instant messaging application with video conferencing capabilities) (note: anybody can join the conference, but only a authenticated user can create new)
• ntfy (unifiedPush distributor server)
• put2post (unifiedPush gateaway for telegram-simple-notifications (used in Mercurygram)