OpenConnect - VPN client compatible with Cisco AnyConnect SSL VPN
OpenVPN - OpenVPN - The Open Source VPN
Pritunl Client - Simple OpenVPN Client and GUI. Additional integration available when connecting to a Pritunl server.
WireGuard - Fast, Modern, Secure VPN Tunnel
Lets VPN - Lets VPN app comes up with features to assist you in enjoying high-speed internet by simply connecting with a multi-national line internet without having to worry about the security of your smart devices.
OpenConnect GUI - This is the GUI client for the OpenConnect VPN, an open-source alternative to Cisco AnyConnect.