The easiest way is to setup tailscale on the server, then share the server with the web interface. Your friends/family simply install the tailscale client, login, and it just connects like magic. No port forwarding or firewall configuration required. There’s plenty of how-tos out there.
Not the simplest to set up, to make accessible, to secure, or for everyone else to use? This solution is a pretty reasonable one considering all four.