Skylark web folder - port change

I’d kind of like to make my Othernet accessible via my web page however my ISP blocks port 80 which is where I the static page shows up (IP Address + :80)

What html program is used? I want to move to say port 90 or something I know my ISP doesn’t block.

You can’t change the port Skylark is served at, but either your router or whatever port forwarder you are planning on usinging to expose Skylark to the external network should be able to map any externally visible port to the internal :80 port.