@iahmad
Why would a user want to type in that URL ?
The (a) captive portal is detected by every OS these days.
I use the captive portal for a hotel, and I do not publish any URL, an certainly not an IP based URL. Still, everybody can login without any assistance from me, or some printed help.
I use https://portal.hotel.tld as the URL that points to the IPv4 of my captive portal interface.
I have to own (rent actually) the domain hotel.tld so I can get a certificate that is trusted by every browser and every device.
All OSs these days do a hidden http (not https) request to a know URL that should return a page that says "Succes". If it doesn't, it kicks of the default browser with the same URL again. The web request gets intercepted a second time, and the result will be the default login page. The user can interact with that page : he/she can login.
For all this to work :
You use https : you need a certificate signed by a trusted source (ie Letensrypt). Otherwise most browsers, if not all, will just don't want to load the page.
DNS on the captive portal interface should work.
On the Services > DNS Resolver > General Settings page I declared a Host Override :
Host : portal
Domain : hotel.tld
IP : the IP of the captive portal
Nothings stops you from declaring something like :
Host a
Domain b.c
So know the user can type in https://a.b.d:800x/index.php?zone=yourzone
The "index.php?zone=cpzone1" part can't be "shortcut".