I have an iPhone XS with two cellular networks configured. I have Verizon service on the eSim and a physical Google Fi sim.
When I have both cellular connections enabled I am unable to get internet via wifi on networks with captive portals.
I connect to the wifi network, which does not have a PSK, and get an IP address, but do not get the captive portal pop-up. My LTE stays on and I can continue to use the internet over cellular. If I disable cellular data or put the phone in airplane more and connect to wifi I get the error about enabling cellular data or connecting to wifi.
I am able to ping the wifi router IP address and when I browse to that IP address I get the hotel's captive portal. I enter my information and then the site times out. The phone still shows connected to wifi in Settings, still has an IP and I can still reach the router, but it is still using LTE for internet.
I have tried resetting the network settings as well as disabling Wifi Assist, but neither of those make any difference.
When I disable the Google Fi cellular service and connect to the wifi I get the captive portal prompt immediately and wifi works as expected. As far as I can tell I don't have any other wifi issues with networks that do not have captive portals, wifi works as expected on fully open or PSK protected networks.
I've searched around and haven't found any other posts with this problem, has anyone else experienced this or have any solutions other than disabling the second cellular connection?