I think the central question here is: .) whether you buy a phone as a piece of hardware and then own that hardware - which gives you certain rights regarding the usage of that owned hardware or .) whether you are just paying some sort of admission fee to a tightly controlled service, and are basically "lent" a piece of hardware that you have no ownership rights over. All the other stuff about walled gardens, monopoli…
As far as I'm concerned if you 'bought' something, it should be yours to do as you please, including reselling and destroying it. If you didn't buy something, but rented it - for example a game on Steam or Epic Games store - then it should damned say so. It's a straight up lie to say you purchased something if you didn't.
You can sell your iphone without any issue, there are plenty of stores around me offering to buy used models to resell. I'm actually contemplating buying a used model. Can't do that with steam games.
I'm also pretty confident that if apple and their services disappeared tomorrow, my iphone would keep on working just like it does today. Sure, no more updates, no more new apps, it would be frozen in the state it's in.
Therefore, I think the question is whether an iphone is a "general computing device", or "an appliance". I can see the arguments for both, even though I tend to treat mine as the latter.