Extender EX6130 does not support open WiFi

I have a EX6130 dual-band wifi extender (interestingly, I couldn't find this model listed in the dropdown list, the 6130 is not present between 6120 and 6150... by the look of it, it's very similar to 6150). I can have it connected to an open wifi which requires a login via HTTPS website, but once the setup is completed I cannot get the login page. All lights are green as everthing is working smoothly. Firmware updated to the latest version.

Tried with a Windows laptop and Android device. Usually, right after connecting to the open wifi I am automatically prompted to provide my credentials: while on Windows, the browser automatically pops up. On Android you've got to tap a pop up notification, then input your credentials.

It looks like the wifi extender is unable (or blocking) any request from the open wifi right before or during credentials are requested.

Customer support couldn't help: they went through the standard manual (the same I've followed) and didn't work. For obvious reasons, I can't access the wifi router so the AP setup isn't a viable option.

I tried a "regular" (smart mode), manual and also Fastlane setup. Tried with and without WPA2 (I'd like to have it as the wifi is open and don't want anyone else connecting to my extended wifi). None worked.

Is it possible to grab the internet configuration (IP address, gateway, subnet mask, DNS, ...) while connected directly to the open wifi and use it as custom setup inside the EX6130 IP address configuration? (I am thinking of everthing at this point).

An older (and for many other reasons, crap) Belkin wifi extender used to work fine with the very same open wifi (the only one available around here...). I don't want to go back to Belkin...

Thanks