GL-AR750S Remote Access

What port or method can I use to get to the router GU remotely


What are you trying to do with / why do you need remote access? The best method will probably depend on your requirements.

I would not recommend you open the UI to the outside directly. Use SSH port tunneling or VPN. That way you are secure and you can block failed login attempts or just to specific clients.

The reason i say that is that the UI is not HTTPS by default, you would have to configure that separately. There is also no brute force prevention.