Looks like they're yet again changing the sign-in experience at United Clubs. This was the new (much better) experience at the ORD F club today.
Just a normal captive portal, no sign-in or anything. The old sign-in portal was notoriously terrible especially on mobile devices (and had a glaring security bug). Glad to see they're moving to just a normal captive portal. Bandwidth certainly hasn't been an issue in clubs for some time.