First of all, there was no announcement from Apple itself about JIT compilation support in iOS 14.2. Documentation for iOS about this manner has not been updated. Whereas macOS allows JIT compilation and in the documentation it is described how to enable this feature. So, it looks like, as far as Apple is concerned, it does not exist for iOS devices yet.
If you read the above article, or other ones about JIT compilation support, they will state that it is for debugging only and that you can’t submit an app with JIT compilation enabled to the App Store. Considering the lack of official documentation about this subject, and by looking into various methods to enable this feature, it makes sense. It’s clearly not production-ready, at least in Apple’s eyes. If it was, they would surely inform us about this.
There is no way to enable JIT compilation and have your app released to the App Store. The fact that Apple is not blocking JIT compilation is, in my opinion, a sign that they are preparing to allow it on iOS devices, and it might be closer than ever before. You might ask when? When Apple thinks it is ready.