How to keep captive portal open on mobile devices?

[sandro87]

Hello,
I'm trying to find a definite way to show a landing page for various hotels after the customer logs in. On iOS the problem is not present, once you're connected the captive portal pop up opens up and after you login if you have a redirect page it will you show up until you manually close it, inside the popup.
On Android after you login the device checks immediately for internet connection at one of their domains and if that succedes the pop up will automatically close. To complicate things more it really depends on the ROM used, some keep it open some don't. Has anyone found a OS-wide way for this? I found this workaround https://stackoverflow.com/questions/34933146/prevent-captive-portal-auto-close-after-authentication-android# but I'm sure I get it and if that proxy thing can be done on OPNsense...