First we need to limit the amount of CPU cores visible to the application and make it think that we are running Windows Vista.

Download the Windows ADK from here:
https://learn.microsoft.com/en-us/windows-hardware/get-started/adk-install

Follow the installation process. You don't need to install the entire ADK but make sure to check the first checkbox in order to install the Compatibility Administrator.

Now we can open the Compatibilty Adminstrator (32-bit).

Under 'Custom Databases' add a new database by clicking the 'New' button to the top left.

Click the 'Fix' button and set the program file location to the full path of your RedFactionArmageddon_DX11.exe file.

Click 'Next' and set compatibility mode to Windows Vista (Service Pack 2).

Click 'Next', enable ProcessorCountLie and set its command line value to 16.

Click 'Auto-Generate' and then click 'Finish'.

Rick-click the database and select 'Install'.

Now we can leave the Compatibility Administrator.

Right-Click the RedFactionArmageddon_DX11.exe file, enable compatiblity settings and set it to Windows Vista Service Pack 2. Click 'Apply'.

We are done. You can now start the game from Steam. Make sure to select DX10/11 in the game's launcher.