I have the same question. My cursory research is:
NO: United Gateway (free) and a United debit card. Those are among the cheapest cards. They have a $10,000 minimum yearly spend
YES: United Explorer (1st year free then $150) and United Business ($150)
YES and expensive cards: United Quest and United Club cards
I need to digest the news more but I think United is basically ending its Mileage Plus unless you are elite or have a mid-level to expensive United credit card. If so, I wonder if they are leaving those semi-frequent business travelers who will one day become a road warrior, college students who can be brainwashed into loyalty in 3-6 years but now only travel 3 times a year. If there is no loyalty among passengers, that might cause them to become basic economy passengers because they will feel that the miles they might get are not worth much. So United might be trying to give fewer miles while Delta Skypesos are legendary for higher award levels.
I had the same question as the poster you quoted. In that context I have no idea what "no" and "yes" mean. The United Gateway card doesn't count as having a UA C/C in the context of the announcement from UA to gut their program and basically require everybody to have a C/C to get the lower redemption rates and higher earn rates? Please help clarify what you meant because the OP you replied to did not ask a yes/no question.
Bottom line...as a UA captive now I want the cheapest (aka free) C/C that gets me the lower redemption rates and higher earn rates with zero or little $ out of my pocket. I have zero intent to use the C/C other than for UA purchases.
Thanks,
-RM