> but general-purpose computing is very much alive and kicking in laptops, desktops, and servers.
Two words: Secure Boot.
The only reason we still can run operating systems without Microsoft's approval on these devices, is that alternative operating systems like Linux were already popular enough when Secure Boot was introduced, so to prevent the risk of antitrust enforcement Microsoft allowed (and AFAIK required) that firmware has an option to disable Secure Boot or enroll your own keys, and Microsoft also signs the bootloader of several Linux distributions (as long as they meet some stringent requirements).
But this can change, since all of that is part of Microsoft's hardware requirements for running Microsoft Windows (which hardware makers must follow if they want their devices to run Windows). And it already has, at least twice: some ARM-based laptops were shipped without that option (the hardware requirements back then were that you must be able to disable Secure Boot or enroll your own keys on x86-based hardware), and a class of devices (the so-called "Secured Core" devices) comes with the "third-party" key, which Microsoft uses to sign Linux distributions, disabled by default. Nothing prevents it from being locked down even further in newer versions of Microsoft's hardware requirements, in the name of "security".