At least those 900 million Windows 10 users have another year before support ends—absent a surprise Microsoft support extension, an affordable support package or a workable workaround. But for 50-million Windows users that end of support nightmare has come true, and Microsoft is warning them of the consequences.

"On new Teams, users on OS versions that are not supported will receive in-app notifications to encourage them to update their device to a supported OS version. A version that is too far out of date will become incompatible with the service and the Desktop client will be blocked until the OS is updated."