With regards to "users being interviewed", there's already a lot of data out there. The interesting thing is that what we currently have is a free market where users are free to make a purchasing decision. Governments are usually reluctant to interfere in a free market.
Do users have a choice of an open system? Yes, they have android/ linux smartphones. Lots of good hardware choices and from numerous manufacturers. These manufacturers often offer handsets free on a plan and there's numerous devices that cost very little.
Do users have a choice of a closed ecosystem? Yes, they can choose Apple. But, they're way more expensive for equivalent hardware specs, are rarely discounted and are never offered for free. The software is more locked down to prioritise consistency, security and ease of use.
Apple's primary business model and what differentiates them FROM THEIR COMPETITION is the closed ecosystem.
So, if the closed ecosystem is allegedly harming consumers, and the hardware/ ecosystem is so much more expensive, why do so many people choose to purchase the iPhone? The free market has spoken, there are users out there who would rather pay a lot more for the iPhone because it offers a consistent user experience, ease of use and security. Not only that, it has scored the highest customer satisfaction ratings in the business every single year since the iPhone was released.
If the Apple ecosystem really was harming consumers, the free market would see that nobody would purchase their products. If the claim is "Apple users can't move because they are locked-in and it's too hard to swap", explain how they still get the highest user satisfaction scores year after year? If these users were dissatisfied and wanted to move but were locked in, how come the user satisfaction surveys don't show that? If the "Open Platform" really was the better option, the free market would choose that, especially if you can get better hardware for a better price. The closed platform HAS TO BE OFFERING ADDED VALUE for consumers to WILLINGLY PAY MORE.
Then the claim that the Apple App Store/ Google Play store is unfairly keeping prices high, which harms consumers. Explain to me why Epic first released Fortnight as Sideload only on Android? They then changed to distribution via the Play store. Users had the choice to install directly by side loading and avoiding any google policies but the majority of users want to install from an App Store so Epic had to release on the Play store. Epic also have their own Epic Games Store on Android, yet users choose to use the play store.
So, when consumers are given the choice of an open platform, a great many choose to pay more for a closed platform. The users that choose an open platform have had the choice of side loading, using the google play store or using the Epic Game store. Despite this, users overwhelmingly prefer to use the Play Store.
I'm not sure how it can possibly be claimed that Apple's/ Google's business model is harming consumers (one of the things needed to be proven in an antitrust case).
Developers are in a contractual business agreement with Apple/ Google and are not classed as "consumers".