That is not true. I just bought this plan by calling AT&T customer service on Oct 22, 2020. I received the device Oct 24 and it was up and running that same day using the self activate feature on myATT. The plan is called Wireless Internet 100GB Triple Play.
Just because you canít find it online means nothing. This plan is available by calling customer service.
I found it with a google search. BIG PROBLEM. It is only available as part of a plan which includes Direct TV.