You probably don't want to use tailscale and other VPN solutions for this, as your friends and any guests would need to install that too to be able to connect.

Do you have a static IP from your ISP?
If so, then as the other commenter said, you only need to set up a port forward to the mumble server running on your network. This is necessary, because that's how you allow certain traffic to reach your server on the internal network. If that Matrix sever is public (internet facing), and federation is working correctly, you probably have a static IP.
If you don't.. well, you would be better off with a domain, then. That's because your IP address will change from time to time, and your friends would always need to correct it. They would get annoyed real quick, I think. But, a domain's purpose is that the computer can look up the current IP address assigned to it, so that should help in that case.