1. Continue their merry way and cede market share.
2. De-enshitify Windows and win back market share.
3. If you can’t beat them, join them. Release a desktop Linux distro.
I believe that while they may aim for option 2, I can’t see it being that successful. Which for me, implies an eventual officially supported Office for Linux (to preserve/grow Office market share by decoupling it from Windows).