Xbox

Xbox (Microsoft) is usually the most accessible console for indies, through the ID@Xbox program. On top of that, any retail Xbox console can be put into Dev Mode, which makes testing easier.

To be evolved. I have no first-hand experience launching on Xbox, the information is general. This section will be completed by a developer with real experience.

In short

You apply to ID@Xbox as a company, Microsoft's program for independent developers.
Dev Mode, you can enable developer mode on a normal Xbox console for testing, without a dedicated dev kit at the start.
After approval: access to the SDK (GDK), documentation and publishing tools.
The game goes through certification before launching on the Microsoft Store / Xbox.

See also Console Platforms for the general context.