You emphasized “all” to imply there are so many, but honestly I can’t think of much beyond what they’re already mitigating to comply with the DMA.
You’ll get a browser selection screen now, other engines will be allowed, default browser choice gets further expanded in terms of implementation so it essentially ensures you never have to touch Safari.
The only thing that is being torn out is PWA installation on Home Screen because it would be yet another significant architectural change that comes with some significant engineering effort during a time of crunch, when the install rate of PWAs is abysmal as it is, even on other OSs.
If Siri would be the one benefiting (which is what you seem to be saying?) then it wouldn’t give Safari an unfair advantage.
No virtual assistants have been designated as gatekeepers under the DMA so preferential treatment of Siri would still be allowed.
That said, to my knowledge Siri doesn’t “learn” from Safari in the sense that it improves or trains on Safari user data.
Instead Safari, and all other apps, including third party apps, can provide information to Siri to be shown during search as well as providing shortcuts so the app can be controlled via Siri.
Users have control over this to a degree so they can exclude information from certain apps.
Alternative voice assistants offer similar APIs to receive information and support voice commands for third party services.
From Apples own documentation I get the feeling that someone discovered that there was no easy way to allow their PWA support to work with other browser engines. Due to a lack of priority, running out of time and general malicious compliance they just nuked PWAs instead of fixing them.
I wonder if the DMA contains some sort of requirement that features not be removed. To force Apple to make PWAs interoperable with other browser engines instead of just nuking them.
or just the features they're motivated not to offer a path to using for other publishers?
(Like, webapp support)