The following information may be confusing to you with acronyms you do not know. If that is the case, take my advice and just get a computer with Windows 11 already on it.
Overview of what I did to make it compatible:
Ensure the mainboard either contains a TPM 2 module or the proc may already have one onboard. It has to be activated in the BIOS. Default is not active.
Make sure the graphics card supports UEFI. In my case, I had to flash the graphics card's vbios to make it possible to boot from UEFI.
Also had to change the Windows 10 root partition from MBR to GPT.
BIOS - set the TPM to active, set the boot to UEFI only, and set Windows OS boot to UEFI.
If you currently have a computer with Windows 10 and have the idea of upgrading to Windows 11, then I wish you the best of luck. When you run the Microsoft app to check whether your computer is compatible with Windows 11, you may get lucky and receive the green checkmark of success. If not, save yourself a lot of heartache and trade in for a new computer with Windows 11 already installed, or hire a professional to "fix" your current computer.
I spent about 6 hours trying to figure out how to "make" my 3 year old desktop computer compatible for Windows 11. The basic overview is, I did a bios update on the mainboard, the cpu, and a vbios update on the graphics card. After numerous reboots and testing various bios settings, I finally figured out that the Windows 10 partition was MBR instead of GPT. That final fix enabled me to boot to Windows 10 using UEFI only. However, the vbios update on the graphics card was also critical. Not so much the mainboard and CPU bios'.
Here is what I have: