Yeah sure. I should specify that I’m only talking about networks with captive portals that require you to log in with a username and password, like those that are sometimes used in hotels where the username is your room number and the password is your last name or something to that effect — this type of authentication is called EAP. If you’re trying to connect to this type of network on your AX1800 in repeater mode, you’ll automatically be asked for a username and password in the gl.inet web interface. If you try to connect to this type of network on your MT3000 in repeater mode, you won’t be able to without tweaking some things and connecting in LuCi instead of the gl.inet web interface.
Now sometimes when you connect to a network with a captive portal you’re redirected to a browser page that forces you to accept terms or sign up to get accosted by spam email for eternity or give the blood of your first born or something, but not provide a username or password. Either router should work with these type of captive portals, but if you’re having any issues make sure you set DNS server to DHCP and disable adguard home if you’re using it. Once you connect to the captive portal’d network via the web interface, you should get a browser pop up in a new tab prompting you to accept the terms or provide your bone marrow sample or whatever, just like if you connected from your phone or laptop directly, and once you do that the router should work as normal.
Sometimes you’ll come across a network that is so bastardized and commercialized that it will be some crazy combination of the two, or a multi-step paywall or something that’s device-specific, like the type of network you encounter on a cruise ship. If this is your case, you’ll probably need to log in with your phone or laptop first, jump through all their hoops there, then copy the MAC address of your connected device and change the MAC address of your router in the web interface to match the one you copied before, then connect the router to the money-grabber’s network and voila it should work like magic.