> Who is allowed to vertically integrate, and who isn't? Under what principle of free markets and user choice? Should users by forbidden from choosing true vertical integration as a design choice? Why?

Vertical integration related to the central communication system in society has been recognized as particularly problematic for quite some time.

> Who is allowed to vertically integrate, and who isn't? Under what principle of free markets and user choice?

There is no 'free market' in any environment that is 'vertically integrated' by a handful of organizations. The very reason why we abolished feudal aristocracy and even went to the extent of doing revolutions and setting up guillotines was to get rid of that kind of environments - which its owners were totally unwilling to let go.

Technological corporate feudalism is as bad as aristocratic feudalism of the yesteryear. They are both based on the concept of property ownership to start with, so they stem from the same concept of private tyrannies where a private tyrant can do whatever it want with what it 'owns' even if it dominates the lives of millions of people.

Developers do jump from Steam. Last I looked I can buy most games on multiple stores/platforms, and Steam is largely a choice the buyer makes.

Apple could totally sell games on Xbox if they wanted: https://www.techrepublic.com/article/xbox-series-s-and-x-dev...

They choose not to.

> What's the delta between a console and an appliance?

The delta is how large and important the mobile phone market is, and the fact that it is a centralized duopoly.

It is perfectly fine to target legislation towards larger, more centralized, and more important markets.

You are also engaging in whataboutism.

Maybe there really are problems with the console market. But regardless of that, we should still take action on the much more important phone market.

> duopoly

Is there some meaningful console I'm missing besides Xbox and PlayStation?

Yes there is.

There is Nintendo, as well as the PC (which is both an open platform and larger than the rest of the platforms combined.)