As far as I can see, Minkah has only missed 3 games during the 4 seasons he's been a Steeler. Not 21. He only played 14 games in 2019. But, he wasn't acquired until two games into the season. So, he played in every game he was on the roster for the Steelers that year. He played a full season in 2020. In 2021 he missed 1 game. And this year he's missed two games with probably another 2 to come following the appendectomy.
I don't know what the Steelers record is in those 3 games.
https://www.nfl.com/players/minkah-fitzpatrick/stats/career