multiSSH

Run one of these on a machine to make it reachable through this proxy. You will be asked for an enrolment password.

Linux & macOS

curl -fsSL https://multissh.erlenberg.net/install.sh | sudo sh

Without sudo it installs for your user only, and is reachable only while you are logged in.

Windows

irm https://multissh.erlenberg.net/install.ps1 -OutFile $env:TEMP\ms.ps1; powershell -ExecutionPolicy Bypass -File $env:TEMP\ms.ps1

Run it in an Administrator PowerShell to install a machine-wide service, or an ordinary one to install for yourself. Saving to a file first is deliberate: piping into iex closes your window if anything goes wrong, and cannot take options.

Then

ssh multissh.erlenberg.net -p 2022

Lists what is connected, and shows each target's host key so you can check it on first connect.