SOGo - SOGo is groupware server with a focus on scalability and open standards.
ProtonVPN - ProtonVPN is a security focused FREE VPN service, developed by CERN and MIT scientists. Use the web anonymously, unblock websites & encrypt your connection.
Baïkal - Cal and CardDAV server
OpenVPN - OpenVPN - The Open Source VPN
Radicale - The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution.
TunnelBear - Really simple VPN to browse the web privately & anonymously.