Answer this 1st. Why would you want to have windows 11 on a core duo and an old motherboard that doesn't support new features that Windows 11 use? Even if and when we do make it to run what will be the benefit to you? What do you hope will happen? Also, the leaked version is a very early beta test version with half of the things missing. Do you want a test build on your PC?
There is a reason for an OS or software to ask for the hardware they do. It means that when it's fully working it will make use of them and if you dont meet the minimum, maybe windows will run but won't run flawlessly and the programs you will run on your windows even less.
Second, if you would have done a small research on what the requirements actually are, you would have seen that Windows 11 ask for a dual-core, 1GHZ minimum so your CPU is not the problem. They need 4GB of ram minimum, a DX12 graphic card, UEFI bios (which you probably have a problem with core-duo class PC), and TPM chip (google again) that old PCs don't have.