It seems like the answer is "no", but … iPhones don't expose themselves as MTP devices when connected to USB?

I'm an Android user, but that just seems like basic table stakes…?

There are some very surprising tradeoffs for being in Apple’s ecosystem. Especially if you’re used to Android.

Let’s just say this: Apple took the time to create a whole different interface for the TRRS headphone jack just so they could have buttons on the headphone cable. Then when app developers thought it was awesome to be able to use that button as a trigger while the app was in the foreground, Apple stopped them by removing their App store listing until the dev submitted a version without that feature. Same with detecting touch size (to ingeniously determine touch pressure).

Is this also possible with music? Got any links on details about that setup?

Maybe also look into unison ( https://github.com/bcpierce00/unison ) instead of rsync so you get 2-way sync :)

From the (currently broken) FAQ [1]: "Sorry, music synchronization with newer devices is currently not supported but if you are a keen developer why not contribute a new service implementation for the ATC Service?"

[1] https://libimobiledevice.org/#faq