The Windows Core OS (WCOS) system is a special version that Microsoft previously prepared for ARM devices. At that time, Microsoft also prepared special versions of WCOS called Polaris and Andromeda.
But later because of various problems, Microsoft has canceled these versions. Of course, these versions themselves have not been developed, so they lack drivers and design.
Recently, Windows Core OS Polaris leaked online. The version is Windows 10 Polaris OS Build 16299. And these versions are ARM32 versions, that is, only 32-bit versions of ARM processors are supported.
The following readme file is the author’s description of the Polaris system, including the adapted equipment and some components.
“This is PolarisOS. It’s a cancelled edition of Windows Core OS that was designed for Desktops and Laptops. This image is early enough to not include much more than the OS itself. It comes with no shell, and won’t load any.
You need an ARM device to boot this, and you need to sideload drivers before first boot. The wim is bootable, but you can also install it directly by applying index 1.
To install on a phone instead of an arm tablet, go to catalog.update.microsoft.com, find the latest firmware for your phone, download all MainOS cabinets for it, place all of them in a folder, and run dism /Image: /Add-Package /PackagePath:
To install on an arm tablet, get the tablet drivers, and run dism /Image: /Add-Driver /Driver: /Recurse
Upon boot, pressing the power button will shutdown the device, connecting the device over USB will expose a diagnostic interface, which you can use to open a command prompt shell afterwards.“
The Polaris and Andromeda systems were originally systems prepared by Microsoft for dual-screen phones and tablets. Of course, this refers to dual-screen Windows devices other than Android.
Later, as you know, Microsoft Surface Duo uses Android instead of using Windows, which is why the Polaris and Andromeda systems were canceled.
Perhaps Microsoft itself realized that it was useless to continue tossing the Windows system on mobile phones, so in the end, Microsoft chose to use Google’s Android system.
The dual-screen tablet Microsoft itself seems to have given up and no longer develop, of course, Microsoft also designed a customized version of Windows 10X for partners.