According to Wikipedia (which is never wrong), Patrick Stewart has been cast in “an undisclosed role” in Doctor Strange in the Multiverse of Madness.
Here Marvel has straight up told people Patrick Stewart is in this movie in some form.
According to Patrick Stewart, though, none of that is happening. he was asked about “his” role in the Doctor Strange trailer by ComicBook.com, and he claimed that’s not him, even though you can hear his very distinctive voice.
It’s all a big tease, but you have to think that Stewart plays a version of Professor Xavier in the film, his character from the X-Men franchise.