There are quite a few solutions to this, many of them discussed on this forum. They all involve some sort of reverse proxy (traefik, nginx, caddy) with or without cloudflare tunnel on top of it.
I personally use traefik to proxy all my docker container (including photostructure). I use a cloudflare tunnel to proxy the traefik endpoints to the internet.
It’s a bit technical… This thread has a lot of details, including a couple of youtube videos on how to do it.
Now @mrm is planning to implement authentication in photostructure. But even when it’s there I would still opt for reverse proxy and cloudflare because I don’t really want to open ports on my firewall.