They didn't take it away completely, but it's now at the flight crews discretion. You can kindly ask a flight attendant to ask the pilot if they will have channel 9 on or ask if they will.
Found this about it[0], but there is still the occasional person asking about it on FF boards and the answer is still, to politely ask the FA about it
[0] https://simpleflying.com/united-airlines-channel-9-story/