I think some troopers recognize him, like the trooper he fights in TFA and the trooper on the Supremacy from the TLJ deleted scene, but I don’t think most would recognize them. It seems like only troopers who knew him personally, or were in the same company/legion as him, have seen his face during day-to-day life.

And it’s possible some knew of his betrayal, or the FO kept it under wraps, but overtime stormtroopers came to learn of his story. Maybe Resistance propaganda pushed that idea and it stormtroopers encountered it in the field.

And I agree with Jar Jar. I think Jannah exclaiming “You?!” could be recontextualized once we imply she’s heard of FN-2187.