Find the Secure Boot option and change it to Disabled. Save the changes and reboot again. We recommend keeping Secure Boot enabled unless you're sure it needs to be disabled. This article explains how ...

TPM and Secure Boot have been some of the reasons why most people could not install and use Windows 11. Microsoft has made some strict hardware requirements and some computers are forbidden from ...

It sounds to me like claiming that all old Windows versions will be unbootable is an overstatement. Rather, it's most likely the case that you won't be able to boot old media when Secure Boot is ...