Probably every pro market eventually and a few college markets, too.
It might very well capture young audiences really well. The Athletic is generally hiring young and will work those young reporters hard, I'm sure. ESPN's ducked out of quite a bit and newspapers spend half of their time asking for permission to do good work.
I'll be curious to see if many younger Athletic writers can write hard things. Real criticism that isn't right out of the liberal millennials' playbook. "It's time to fire Coach X because he called an escort service" is an easy opinion. "It's time to fire Coach X because he can't manage the clock" seems easy, but it usually isn't, because most young writers would just as soon write 2,000-word feel-good features about this pro player's charity or this college player's single mom, or what have you, then **** off some coach.
And I'll be curious to see where The Athletic falls. Fans are fans, and they want sugar when warranted, and blood the rest of the time. Journalists are journalists, and like to win awards and colleague approval through takedowns of the most obvious villains or paeans to the 24-year-old who's changing the world, one home run at a time.