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.
A manufacturer cannot dictate the consumer's options regarding the owned devices, even though they have it in their terms and conditions. Apple is currently being gobsmacked by right to repair claims under this very principle.
>Apple makes the devices, they are 100% legally allowed to only allow apps from their own App Store and that precedent has already been set.
This is false. As proven time and time again, the Device Owner has full legal control after purchase.
It is monopolistic behavior due to the scope of the control from Apple. The devices are the owner's property, and it is monopolistic for them to implement software/policies/hardware blocks, that prevent users from using the devices as they see fit.
Take a simplistic example, Keurig. Keurig tried to prevent users from using any other coffee pod besides theirs. There is precedent to these monopoly lawsuits.
https://time.com/2913062/k-cups-war/
https://topclassactions.com/lawsuit-settlements/consumer-pro....