You can still install Windows 11 without a Microsoft account. It requires configuring the installation before you boot from the USB stick.

I use https://rufus.ie/en/ when creating bootable USB sticks, and it turns out that this tool detects when you're trying to create a Windows installation medium, and prompts with a list of useful customizations, including "Remove requirement for online Microsoft account". (if you look through the screenshots on the webpage, there's one with the Windows customization dialog box)