Navigate to Tools > Settings and enable "game source" and "DX12"
Navigate to settings
Enable game source and DX12
Restart XSplit.
Restart the application
Add a Game capture source and select "Streaming Avatars".
Stretch it to be full screen (ideally that is the same size as the stream avatars window for pixel perfect graphics)
Set the background color of stream avatars to match the background removal Color Key of XSplit.