SSH Tunnel Manager (STM) is described as 'SSH Tunnel Manager is a macOS application to manage your SSH tunnels. If you don't know what that is, quite honestly, maybe you don't need SSH Tunnel Manager, but if you appreciate the power of connecting together two networks using the SSH protocol, then STM is for you'. There are five alternatives to SSH Tunnel Manager (STM) for a variety of platforms, including Windows, Linux, Mac, BSD and PortableApps.com. The best alternative is PuTTY, which is both free and Open Source. Other great apps like SSH Tunnel Manager (STM) are OpenSSH (Free, Open Source), Snowflake (SSH / SFTP client) (Free, Open Source), Shell NGN (Freemium) and Putty for Mac (Paid).
PuTTY is a free and open-source terminal emulator, serial console and network file transfer application. It supports several network protocols, including SCP, SSH, Telnet, rlogin, and raw socket connection. It can also connect to a serial port.
OpenSSH is a free version of the SSH connectivity tools that technical users rely on. OpenSSH encrypts all traffic (including passwords) to effectively eliminate eavesdropping, connection hijacking, and other attacks.
Putty is one of the Best Terminal Emulators available today. It Supports different types of Network Protocols such as SSH, FTP, SCP, Telnet etc. In Windows it is used as SSH Client to connect to Your Linux server or for some other purpose.