I don't think that the translation feature itself can be considered OS functionality. An API providing on-demand background execution time for apps linked to connected Bluetooth devices would surely be sufficient to comply with the DMA?
As an example, when they were compelled to allow competing browser engines, they didn't open source Safari; they added a multiprocessing/JIT API to iOS (tailored and restricted by policy to browsers). Competitors (web browsers) got access to the OS features (multiprocessing/JIT) that they needed to compete with Apple's product (Safari), but they didn't get access to the product itself and still need to build their own.
In this case, competitors (device makers) might request access to the OS feature (background execution) that they need to compete with Apple's product (live translation on AirPods).
It should also be noted that such functionality only has to be provided if explicitly requested by a developer who is working on a competing product, so they don't have to develop it preemptively.
I'm not saying that this is completely fair or whatever, just that I don't think it's quite as extreme as people are making it out to be?
As an example, when they were compelled to allow competing browser engines, they didn't open source Safari; they added a multiprocessing/JIT API to iOS (tailored and restricted by policy to browsers). Competitors (web browsers) got access to the OS features (multiprocessing/JIT) that they needed to compete with Apple's product (Safari), but they didn't get access to the product itself and still need to build their own.
In this case, competitors (device makers) might request access to the OS feature (background execution) that they need to compete with Apple's product (live translation on AirPods).
It should also be noted that such functionality only has to be provided if explicitly requested by a developer who is working on a competing product, so they don't have to develop it preemptively.
I'm not saying that this is completely fair or whatever, just that I don't think it's quite as extreme as people are making it out to be?