EDIT: Oh… I just realized you asked how it DIVERGES from PbtA, not how it is similar to PbtA. lol my bad. I'll come back with a more informed response later!

So far I can confidently tell you that the Player Principles in Daggerheart are very much like the Principles of Apocalypse World:

• Be a fan of the character
• Address the characters
• Look through crosshairs
• Play to find out what happens

In other words, it gives clear guidance on what it means to be an MC/GM. It's explicit about not railroading. It's explicit about not pulling the rug underneath your players ("Oops! You didn't check for traps! That's 999999 bludgeoning damage coming your way!"). I like when games are this explicit; it's easier to have a conversation about what good and bad GMing looks like.

I also know that it doesn't just have success and failure (and critical successes and failures). Instead, it has successes and failures that aren't as extreme, so small complications pop up more often.

The character progression checklist also looks straight up from an Apocalypse World character sheet (in a good way!). [Edit 2: I learned that the checklist might be similar to Apocalypse World, but there's this whole card system where each level involves choosing new feats or abilities or things like that, all related to your class]

Look also to one heir of PbtA: Blades in the Dark.I'm biaised, I like mist of this game (including Deep Cut).

What is PbtA? Well, the Baker's definition:

"Powered by the Apocalypse" isn't the name of a kind of game, set of game elements, or even the core design thrust of a coherent movement. (Ha! This last, the least so.) Its use in a game's trade dress signifies ONLY that the game was inspired by Apocalypse World in a way that the designer considers significant, and that it follows our policy wrt others' use of our creative work.

Is Daggerheart inspired by Apocalypse World? I think so: Meguey Baker co-authored Apocalypse World and the post-apocalyptic "Motherboard" campaign frame in Daggerheart. I would be surprised if Mercer would not have credited PbtA somewhere. If Darrington Press would like to, Meg and Vincent would probably approve with the "PbtA" stamp.

It doesn't use the "2d6+stat" role mechanic but that is not essential just like all the other game mechanics.

I'm sorry. This is probably not very helpful. Maybe a more precise answer could be given if you ask how it diverges from "Dungeon World" or some other PbtA game you know.