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I am not sure if Apple should extend it's chip design business. It looks that M1 / M2 will be outperformed in March by new AMD designs, now that AMD also uses 4nm technology for building chips. So Apple will need to step up here to stay competitive.

Now the App Store is the single gatekeeper regarding to policies and monetisation.
Policies are made by Apple and some (good, bad and ugly) governments.
It will be interesting to see if governments will loose the power to dictate policies when App Stores become fragmented.
I am not very much concerned regarding security – this is up to iOS, the App Store was more or less only good for revoking developer certificates (disabling apps) when an app used an exploit found in a version of iOS.

Since nobody is forced to use a third party App Store this is a good thing. Personally I believe that iOS (and iPadOS) are much more important for security than the App Store and that the App Store is more about policy (and money).

Best thing one could do now ...

I believe it's only relevant if someone allows apps (to ask for) tracking from the iOS Settings and then allows the app to use Ad IDs.