Tap here to sign in to network
After dicking around in ADB with Captive Portal setting, changing URLs and crap, I finally just gave up and set :
adb shell settings put global captive_portal_mode 0

now it doesn't check, doesn't prompt to login to a non-existent portal, or show &quot;No Internet&quot; on the wifi - and the wifi does work.
Don't know WTF was going on, but I wasted an entire day screwing around with this stupid phone.