Captive portal

I have gl-inet 4g smart router.
I wanted to setup a captive portal on this, so, that when someone connects to this WiFi, they will be redirected to a landing page first.
Can someone please help me to understand which is the free captive portal tool i can use ? i tried with nocatsplash. But i think there is some config mismatch. Anyone got any experience in this ?

Thank you,

I always used coova-chilli. Which usually needs a backend server for freeradius.
coova-chilli is the most flexible CP (Captive Portal), also used in commercial installations, but it has a steep learning curve, as quite some docs flaoting around on the web are outdated.
nodogsplash might be simpler alternative.

Thank you.
I was trying to bringup nodogsplash. Mine is an AP now.
i am using it as a repeater by connecting it with the WiFi.

when i try the IP address of the device, i.e, i get the nodogsplash screen.
I want to achive the same with all which connects to the SSID.