They already have a Windows version for a handheld. The Xbox runs a modified version of Windows 11. All they’d need to do to bring it in line with PC handhelds is allow the install of third party launchers (they probably wouldn’t do this though).
i think they are already mentioning it: MS has a help webpage on how to install linux, both WSL2 on Windows machine, or how to burn iso and install linux on bare metal. https://learn.microsoft.com/en-us/linux/install
Microsoft have quite a bit of software that runs on Linux (PowerShell, VS Code, .NET, Azure tools, Intune / Endpoint Manager, even SQL Server) so it's understandable that they'd have documentation to explain it to their customers.
Yep, they run it themselves even. Previously their motto was "Linux is a Cancer" now they have embraced it and developed their own distro (CBL). With how everything is going WebApp these days, I can see a day when Windows will be linux based kernel.