A non-Apple computer with MacOS installed is commonly referred to as a Hackintosh. And they do exist. You just need the right combination of components and some modifications to the software. But these do not comply with the MacOS End User License Agreement. So you can not sell Hackintoshes or help others build them without violating this. It can therefore be hard to find information about these or official support for this.
However there is nothing in the EULA of Windows saying you can not install in on an Apple computer, nor anything in the Apple computer EULA saying you can not install Windows on it. As you say it is officially supported in Boot Camp.
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