>has the legal right to install whatever they wish

Absolutely. But people buy the devices knowing that that's not an option. It's not like Apple locked down these devices and changed them after people bought them. You can absolutely jailbreak your device and put whatever you want on it and I fully support that. That doesn't make Apple's behavior monopolistic or an anti-trust violation.

Your Keurig example isn't relatable or similar at all since Keurig both did have a monopoly on single-use coffee pods and that was the single purpose of the device. An optional App Store is not the same thing at all.