You can do this with mumble easily. Set up one pi as a mumble server, and one pi as a client. Then, the router where the mumble pi server is connected, enable DynDNS. Set up an account on either DynDNS or NoIP. Watch YouTube for examples. On the pi client, have it connect to the address of NoIP (or DynDNS). This…

You should definitely read the Linux command line and shell scripting Bible. It’s a really good read, and I always go back to it to refresh on things I forget. https://www.amazon.com/Linux-Command-Shell-Scripting-Bible/dp/111898384X