If it isn't on the supported processor list, it will show up as not compatible.
This specification details the Intel processors that can be used with Windows 11 customer systems that include Windows products, including custom images.
docs.microsoft.com
Microsoft doesn't really care if you install Windows 11 on a system with an incompatible processor, but they insist that you do so at your own risk. Other restrictions, such as TPM version 1.2 minimum, still apply.
Learn how to install Windows 11, including the recommended option of using the Windows Update page in Settings.
support.microsoft.com
Ben