Router gets the public IP. Login to it, find port forwarding option. You’ll pick a public port. IE 443 and forward it to a local IP:port combo, IE 192.168.0.101:443.

Then you can pick another public port and forward it to a different private IP:port combo.

If you want a subdomain, you forward one port to one host and have it do the work. IE configure Nginx to do whatever you want.

EDIT: or you use IPv6. Everything is a public IP.

Back in the WEP/WPS days it was easy enough to use aircrack-ng and get access to a network. Anything public is likely to be slow and probably no access to open ports or manage it in any way.

I’m paying ~$45 CAD/month for a symmetrical 500Mbps line and I think its worth it. I’d never share this with anyone I don’t know because my name is on it, anything anyone does will come back to me.