ZTNA supports SSH connection rules that allow remote workers to access SSH servers inside the network through an HTTPS tunnel between the client and the access proxy (FortiGate). The access proxy acts as an SSH client to connect to the real SSH server on behalf of the user, and performs host-key validation to verify the identity of the server. The user can use any SSH client that supports HTTPS proxy settings, such as PuTTY or OpenSSH. References:https://docs.fortinet.com/document/fortigate/7.0.0/ztna-deployment/899992/configuring-ztna-rules-to-control-access

https://docs.fortinet.com/document/fortigate/7.4.1/administration-guide/29927/ztna-ssh-access-proxy-example