> One day their data was on the local drive and the next it became online-only files that had to be downloaded from Microsoft’s servers.

That is insane. If this happened to me, there is zero chance I would continue using that product. If something like this happened to my parents, I'd make them switch off windows if they wanted help with their computers (which I already did for other reasons, and the result was immensely positive, though the target OS was macOS, not linux.)