If you have a PC connected to a router by an Ethernet cable or Wi-Fi

you can do port forwarding

You can purchase a DNS domain and have it point to a DDNS hostname.

A DNS domain and DDNS hostname are static.

The static DDNS hostname points to a dynamic public IP given by a router.

A DDNS IP updater updates the dynamic IP automatically

The PC has a service listening on an internal port, that port is redirected from an external port using “port forwarding”

If you have a web server, you can purchase and install an SSL certificate.