Airing on Hulu (US) or Disney Plus (outside US) - Monday, September 18, 2023 at Eastern Time (ET) 03:00 a.m/ Pacific Time (PT) 12:00 a.m
ChatGPT was made available to the public in November 2022, when they were still in production. I don't know enough details to say whether that was enough time to get a script in for one episode. It's possible they used something before ChatGPT, since similar tools have been around for several years, just not as advanced or accessible as ChatGPT.