As said in the thread, you need some kind of tunnel that stays up and doesn’t need to be fixed if the internet goes down.

Wireguard, or if wanting super easy setup, Tailscale version of Wireguard great for this. Now you have a private IP address in your VPN network to your home server, that stays up and answers to HTTP. Next thing you need is a cheap VPS somewhere with a public IP address. When that is running, and its in the Wireguard network so you can access your home server from the VPS, you need a Nginx proxy in the public server. Either do it by hand, or use a service such as the Nginx Proxy Manager to handle the proxy setup.

How it basically works is you register a domain name (A, CNAME) to the public VPS service, then with Nginx you setup that anything coming in to the domain X should be proxied to the VPN IP address Y and port Z. Now you can add HTTPS to this domain and get a Let’s Encrypt certificate for it. You can, again, do this manually with Nginx, or let Nginx Proxy Manager handle it for you.