Installing Linux side by side on a Windows machine, was and still is simple.
However, now a days there is one more / extra step before installing Linux(specifically Ubuntu) on a Windows machine. Now a days the hardware and the boot option comes with a setting called Secure Boot. This option is by default it is enabled for a new laptop running on Windows 11. This is to make the system secure at boot level and Windows 11 requires this option to be available in order to be installed on the system.
Trying to install Ubuntu in a system like this will fail. This is because Secure Boot will not allow anything to be changed at that level.
Disable Secure Boot. Before installing Ubuntu.
And then try installing Ubuntu and everything is all good. Windows and Ubuntu will still work, only thing is the Secure Boot is available but disabled.
References of Secure Boot
- What is Secure Boot and how it works?
- How to disable Secure Boot
- Microsoft. Disabling Secure Boot