> This is only true if you use Secure boot. [...] so should be turned off. Then any OS can be installed.
You can only turn off Secure Boot because Microsoft allows it. In the same way Android has its CDD with rules all OEMs must follow (otherwise they won't get Google's apps), Windows has a set of hardware certification requirements (otherwise the OEM won't be able to get Windows pre-installed), and it's these certification requirements that say "it must be possible to disable Secure Boot". A future version of Windows could easily have in its hardware certification requirements "it must not be possible to disable Secure Boot", and all OEMs would be forced to follow it if they wanted Windows.
And that already happened. Some time ago, Microsoft mandated that it must not be possible to disable Secure Boot on ARM-based devices (while keeping the rule that it must be possible to disable it on x86-based devices). I think this rule was changed later, but for ARM-based Windows laptops of that era, it's AFAIK not possible to disable Secure Boot to install an alternate OS.
You can only turn off Secure Boot because Microsoft allows it. In the same way Android has its CDD with rules all OEMs must follow (otherwise they won't get Google's apps), Windows has a set of hardware certification requirements (otherwise the OEM won't be able to get Windows pre-installed), and it's these certification requirements that say "it must be possible to disable Secure Boot". A future version of Windows could easily have in its hardware certification requirements "it must not be possible to disable Secure Boot", and all OEMs would be forced to follow it if they wanted Windows.
And that already happened. Some time ago, Microsoft mandated that it must not be possible to disable Secure Boot on ARM-based devices (while keeping the rule that it must be possible to disable it on x86-based devices). I think this rule was changed later, but for ARM-based Windows laptops of that era, it's AFAIK not possible to disable Secure Boot to install an alternate OS.