I remember hearing Sk8er Boi on alternative stations. It was one of those weird songs that could totally fit the alternative sound, kind of sounded like Paramore, but many alternative stations wouldn't have touched it because she was promoting as a pop star. Had it not been for that fact, it would have worked. For that matter, Miley Cyrus and even Taylor Swift have put out a song or two that might blend well with alternative if not for the fact that they were being promoted as pop. So on that note, maybe Harry Styles CAN work as alternative....I just see that song as too melodic pop to work, but "As it was...." I've been a listener to alternative since I was a teen in the 80s, and there were a few artists that were worked to alternative (or whatever it was known as back then) because nobody was sure how to classify them. I had even heard that very early Madonna "Burnin' Up" was even given some alternative airplay initially, but once she was classified as pure pop, out she went. It would be nice for alternative to just play songs, even by pop artists, if they don't exactly play as mainstream pop, but for the most part alternative refers more to artists than songs.
I do remember "Without You" by The Kid Laroi from a couple of years ago getting those spins on alternative but was the Miley version also playing on alternative? Taylor Swift on the other hand has paired up with indie rock band The National on a couple of songs with some spins on Triple A, including their newest song "The Alcott," but don't know if that would also be added on alternative too. I guess any band/artist is possible to be added on alternative. Since the 2000s, I've seen Katy Perry, John Mayer, One Republic, 3Oh3, heck even BTS made it on alternative when they collaborated with Coldplay's "My Universe" song. At this rate, I wouldn't be surprised to see Beyonce or The Weeknd ending up at least once on alternative.