I install a reverse proxy on every remote machine (raspberry pi or odroid) I manage. These machines are usually tucked behind someone's router, and it is hard to tell every router owner to forward the ssh port. When I install a reverse proxy, the machines can proactively tunnel right into a beacon machine whenever they are online and I can ssh into them from the beacon machine directly. I usually set up frpc as a service on the remote machine. It is also possible to use autossh with a monitoring port for this, but I noticed that frpc can bypass firewall restrictions much easier. This scheme also lets me use tools like Cockpit to view the health and status of my remotes.

https://github.com/fatedier/frp