According to my exhaustive research (i.e., Googling it), the only time an MLB pitcher threw a no-hitter in his MLB debut was Bumpus Jones of the Cincinnati Reds in 1892.
Well it happened again in my Rays save on July 1, 2023:
And here's what makes it really weird with Fitterer: He threw 144 pitches, striking out 10 and walking 5, but the guy isn't even really a starting pitcher! Note his stats coming in over the last couple of seasons:
The guy was basically a relief pitcher, and the AI had him throw 144 pitches, so I expect to see "injury, diagnosis pending" after his next start.