One thing people underestimate is how little these offices tend to need. You can keep a couple Win95 machines around to run your warships and fax machines, but all the pencil-pushers and spreadsheet jockeys can switch to Debian and Libreoffice without much of a hitch. As long as Slack and Chrome runs, they're not going to have much trouble in today's workplace. At the going rate, GNOME might be easier to use than iPadOS, and many workers know GSuite better than O365.
The question is - how does Microsoft lure them back? Contracts, no doubt. But many of these places will probably seek self-sufficiency outside US cloud providers, so Azure better be priced to move.