Microsoft can distribute their Windows Desktop Environment for Linux in a repository they control. And that repo can even contain just the binaries, with their own proprietary licence. These packages can further have dependencies to other open source packages.

If Microsoft ends up with their own Linux distribution or just mirrors an existing distro (like what Alma/Rocky does with RHEL, or Ubuntu with Debian) ... That depends on how much control they want over the Linux distro base OS.

But they certainly have the possibility to add a Windows experience as an alternative to GNOME, KDE, Cinnamon, XFCE, etc, etc, building on top of a shared base OS layer. As well as providing WINE like layers to make existing Windows programs run in that environment.